You’ve seen a lot of flat bags in your daily life and at the supermarket, right? They’re used to package a variety of products, such as snacks, daily necessities, seasonings, parts, and more. In this article, we’ll introduce you to the most common flat bags in our daily lives.
What is a Flat Bag?
Flat bag is very common and simple plastic bag. Flat bag is plastic bag with a completely flat surface and no side gussets. It is typically heat-sealed on the sides or back, and when fully unfolded, it resembles a flat sheet.
Key Features
Simple Structure: It consists of two sheets (or a single sheet folded in half) of plastic film sealed at the sides and bottom, with an open top.
Lowest Cost: Due to its simplest manufacturing process and relatively low material requirements, it is the lowest cost of all bag types.
Unable to Stand on Its Own: Because the bag is flat, it cannot “stand” on its own and usually requires the support of its contents.
Large Printing Area: The flat surface of the bag provides a good, continuous printing area.
Common Uses
Food Bags: Used for packaging bread, fruit, vegetables, etc.
Industrial Packaging: Used for packaging small parts, hardware products, etc.
Inner Packaging for Electronic Products: Used for storing accessories, instruction manuals, etc.
What are the types of flat bags?
Back-seal bags have a sealed edge on the back.
This is the most common type of flat bag.
Side-seal bags and double-seal bags have a sealed edge on each side, with no seal on the back.
Apparel, publications, posters
Three-side-seal bags have sealed edges on both sides and the bottom, but are open at the top. This is another name for a back-seal bag.
On this basis, flat bags can also be made into various forms such as punching, zippers, handles, etc.
What are flat bags typically made of?
Material Type Characteristics Common Uses
HDPE (High-Density Polyethylene): Has a hard feel and a rustling sound, commonly used for supermarket vest bags and garment bags.
LDPE (Low-Density Polyethylene): Soft, tough, and transparent, commonly used for food packaging (such as bread bags).
PP (Polypropylene): Extremely transparent, brittle, and smooth, it allows for beautiful printing effects and is often used in high-end clothing and gift packaging.
Degradable materials (such as PLA/PBAT): Environmentally friendly materials that degrade under certain conditions and are used as alternatives to traditional plastics.
Sizes: Available from a few centimeters (such as electronic component bags) to over a meter (such as large shopping bags).
Thickness: Typically measured in “wires” (C) (1 wire = 0.01 mm). Common ranges include:
Ultra-thin: 1.5C – 2.0C (supermarket roll bags)
Regular: 2.5C – 4.0C (ordinary shopping bags)
Thick: 5.0C – 8.0C (durable tote bags)
Flat Bag Making Machines
Vertical Form Fill Seal (vffs) Machines
This is the most common type of flat bag production equipment. Most of the snack bags, daily necessities, and other product bags we see are made with this type of machine.
Workflow:
Unwinding: The film roll is unwound.
Folding: The flat film is precisely folded in half by the machine’s former.
Side Sealing: The heat-sealing blade heat-presses the two sides of the folded film together, forming two vertical edges.
Bottom Sealing and Cutting: A transverse heat seal knife simultaneously seals the bottom (forming the top of the next bag) and cuts the previous bag.
Counting and Output: The finished bags are counted and stacked for output.
FAQ About Flat Bags
Q:What is the difference between flat bags and gusset bags (stand-up pouches)?
A: The main difference lies in the bag structure:
Flat bags: The bag is flat and cannot stand on its own; it needs to be held open by the contents. They are the lowest cost.
Gusset bags: They have gussets on the sides or bottom. When opened, they provide a larger volume, can hold more items, and can sometimes stand on their own.
Stand-up pouches: They typically have a bottom gusset and can stand directly on the shelf like a bottle. They have a high-end appearance but are the most expensive.
Q:What products are suitable for flat bags?
A:Small, flat or regular items. The product itself fits easily into the bag, keeping it flat for easy stacking and display. Of course, if you would like to know if your product is suitable, please contact us directly with your product information and we will help you determine and develop a suitable packaging solution free of charge!