What Is a VFFS Bag Forming Set and How Does It Work?

Введение

Every snack bag, coffee pouch, and sugar sachet you see on a supermarket shelf was shaped by the same component: a VFFS bag forming set. It is the part of the packaging machine that turns a flat roll of film into a tube — and without it, the rest of the machine has nothing to fill or seal.

For packaging machine manufacturers and spare parts wholesalers, understanding how a forming set works is step one. It tells you what to look for, what to specify, and why precision matters more than price when sourcing this component.

What Is a VFFS Bag Forming Set?

A VFFS (Vertical Form Fill Seal) bag forming set is the tooling assembly that shapes flat packaging film into a continuous bag tube on a vertical packaging machine. The three core components are:

• Forming shoulder (also called forming collar) — the curved ramp that guides the flat film as it wraps into a tube
• Forming tube — the central mandrel that defines the bag shape and diameter
• Film guide elements — tensioners and guides that keep the film tracking straight without slack or drift

How Does It Work? The 6-Step Cycle

1. Film unwinds from the roll and feeds upward over the forming shoulder.
2. The shoulder curves the film downward and wraps both edges around the forming tube, bringing them together at the back seam.
3. A vertical sealing jaw fuses the back seam — either fin seal (inner-to-inner) or lap seal (inner-to-outer).
4. The tube travels downward. A horizontal jaw seals the bag bottom.
5. Product fills from above, through the forming tube, by gravity.
6. A top seal closes the bag. A cutter separates it. The cycle repeats — up to 300+ times per minute.

The forming set guides the film through every one of those cycles. A shoulder that is off by 1 mm will cause film drift, back-seal wrinkles, or tears before most operators can locate the cause.

Two Types: Collar-Type and Trunk-Style

Collar-type forming shoulder: The universal standard. Handles granules, snacks, seeds, coffee, and any free-flowing dry product. Available in round, square, oval, and gusseted formats. Film width range: 35mm to 800mm. Browse our VFFS Bag Former range.

Trunk-style forming tube: A specialist variant with an extended tube that delivers product to the bottom of the bag before the seal zone closes. Essential for powders and liquids where seal contamination is the main quality problem. See our Trunk-Style Former page.

Not sure which type fits your machine? We cover the full comparison — product by product — in a separate guide.

Teflon Coating: Three Options, Each Solving a Different Problem

Friction between the film and the forming shoulder is one of the most common root causes of film breaks, static build-up, and material clogging. Our workshop applies three types of Teflon treatment:

Customization: 35mm to 800mm

Off-the-shelf forming sets only fit standard machine models. Our factory machines custom forming sets across the widest range in the market:

• Film width: 35mm (narrow sachet lines) up to 800mm (wide flat-bottom pouches)
• Bag shapes: round, square, oval, gusseted, quad-seal, triangle / pyramid
• Compatible with all major VFFS brands: Dasong, Coretamp, Baopack, Zhongke, and more
• OEM/ODM available — manufacture under your brand
• MOQ: 1 piece for custom orders

Ready to go deeper? Now that you know what a forming set does, the next question engineers always ask is: how do you design one — and what makes one forming shoulder better than another?

We answer that in detail in our next article: How to Design a VFFS Forming Shoulder: Key Considerations. If you would rather go straight to our products, visit our VFFS Bag Former page or our Trunk-Style Former page to explore specifications and request a quote.