Gusseted Bag Making Machine: How In-Line Side Gusseting Works

A gusseted bag making machine folds the sides of plastic film inward to form expandable side panels before the bag is finished. Side gussets help a bag accommodate bulkier contents without requiring the entire bag to be made wider.

This guide explains how side gussets are formed, the difference between pre-gusseted film and in-line gusseting, which bag dimensions to specify, and which COSMO machine configurations support the process.

What Is a Gusseted Bag Making Machine?

A gusset is a fold along a bag’s side. When the bag opens, the folded panel expands to provide additional depth. A side-gusseted bag is therefore different from a bag with a bottom gusset, where the extra material is folded into the base.

A side gusset bag making machine may form these folds in-line, depending on its configuration. Side gussets can be used on T-shirt bags, bottom-seal bags and certain bags-on-roll products. The finished bag format determines whether the line cuts and stacks bags or produces perforated bags on a roll.

See also: Types of Plastic Bags: Materials, Seals and the Machines That Make Them

How Are Side Gussets Formed During Bag Production?

There are two practical ways to supply side-gusseted film to bag production.

Pre-gusseted film: The film tube is folded at an earlier stage, such as during blown-film extrusion, and arrives at the bag making line with the side folds already formed. Whether this is suitable depends on the intended bag and the equipment configuration.

In-line gusseting: A gusseting unit forms the side folds during the bag-making process. COSMO offers side-gusseting configurations on several machine platforms.

Some of our COSMO models also include a hot slitting unit. Hot slitting and gusseting are separate functions: hot slitting processes the film lengthwise, while gusseting forms the side folds. The required combination and compatible film feed depend on the selected model and finished bag.

For example, the ST-88-D2 has a side gusseting unit. If you need a T-shirt bag making machine with hot slitting and side gusseting, the ST-88-G2/G3/G4 series offers two-, three- and four-line configurations. For multi-line bag production, refer to each model’s product page and confirm the film feed arrangement for your bag.

T-shirt bag samples for COSMO’s ST-88-G2+AP / ST-88-500-G2+AP

Watch: COSMO Two-Line T-Shirt Bag Machine with Hot Slitting, Side Gusseting & Auto Packaging

How to Measure a Side-Gusseted Bag

Before comparing machines, identify the dimensions on a finished bag sample or technical drawing:

• Face width: The width of the bag’s front panel, using the measurement convention shown on your drawing.
• Side gusset: The depth of the folded side panel. State clearly whether the figure refers to one opened side panel, the flat tuck depth, or a combined measurement.
• Bag length: The finished length, including any handle or seal allowance where relevant.
• Film thickness and material: Specify the film type, nominal thickness and any printing requirements.

Confirm the required film width with COSMO using a dimensioned bag drawing or sample. Specify whether each gusset dimension refers to the flat tuck or the opened side panel, and ask how it relates to the published “Bag Width” range for your selected model.

Which COSMO Machines Support In-Line Gusseting?

COSMO offers side-gusseting options across several bag-making formats. The table below is a configuration overview, not a substitute for each machine’s published specification sheet.

Watch: STBCR-40-G2+OS+2W T-Shirt and Bottom-Seal Bags-on-Roll Demo

For detailed bag-width ranges, film thickness, roll capacity, line speed, utilities and dimensions, refer to the individual COSMO product pages. These figures differ by model and should not be treated as changes caused solely by adding a gusseting unit.

See also: How to Choose the Best Bottom Sealing Bag Machine: A Practical Buyer’s Guide

What Should You Check Before Choosing a Configuration?

• Finished bag requirements: Confirm whether the order calls for T-shirt bags, bottom-seal bags or bags on a roll. Provide a sample or drawing showing the side folds and finished dimensions.
• Incoming film format: Confirm whether the film will arrive as pre-gusseted tubing, flat tubing or another feed arrangement. A model with hot slitting should not automatically be assumed compatible with every incoming film format.
• Machine and utility requirements: Compare the number of lines, film-roll limits, available floor space, power supply and compressed air against the published specifications for the exact model being quoted. Specify any automatic packaging or die-cutting requirements separately.

See also: T-shirt Bag Making Machine: The Complete Selection Guide

Gusseted Bag Making Machine FAQs

Do all gusseted bag making machines need hot slitting?

No. COSMO lists the ST-88-D2 with a side gusseting unit, while the ST-88-G series combines hot slitting with side gusseting. The required configuration depends on the film feed and finished bag.

Can I use pre-gusseted film instead of forming the gusset in-line?

Pre-gusseted film is one way to supply side folds before bag making. Whether a particular COSMO model can process that material should be confirmed against its feed configuration and your bag specification.

How should I specify gusset depth?

Provide a drawing or physical sample and label whether the dimension is the flat tuck depth or the opened side-panel depth. Avoid using “total gusset” without defining exactly what is measured.

Can a gusseted line make bags on a roll?

Yes. The SCR-40-G2 is a gusseted bags-on-roll machine with hot slitting, side gusseting and cores. Specify the finished bag format and core requirements before selecting a model.

See also: Bags-on-Roll Machine Buyer’s Guide: Specs & 18 Models Comparison

Why Choose COSMO

COSMO offers side-gusseting configurations across T-shirt, bag-on-roll and bottom-seal platforms. This range lets us recommend a line around the finished format you need, whether bags are stacked, supplied on rolls with cores or finished with die-cut handles.

The ST-88-D2, ST-88-G2/G3/G4 and SCR-40-G2 include standard servo drives and automatic stops for film runout, film-feed blockage, bag jams and missed color marks. Depending on the selected model, the range also includes automatic core changing, in-line packaging or die-cutting, so these requirements can be considered alongside your bag and film specifications.

Find the Right Line for Your Side-Gusseted Bags

For a recommendation tailored to your side-gusseted bags, send us a sample or dimensioned drawing showing the face width, bag length and clearly defined side-gusset measurement. Include the film material and thickness, printing or registration requirements, and incoming film format and roll details.

Tell us whether you need stacked bags or bags on a roll, with cores if required, along with your target production requirement, available utilities and floor space. We will review these details with you and recommend a suitable COSMO model and configuration.

Request a gusseted bag making machine quote and explore our e-catalog.