Introdução
When sourcing a VFFS bag former — whether you are a machine manufacturer equipping a new line, or a wholesaler restocking spare parts — the first decision is always collar-type or trunk-style. The wrong choice means the former either cannot handle the product, or the machine runs at a higher rejection rate than it should.
This guide breaks down the selection decision product by product, so you can make the right call in minutes.
Not yet familiar with forming sets? Start here: What Is a VFFS Bag Forming Set and How Does It Work?. Or if you are already seeing problems on your line: 5 Signs It’s Time to Replace Your VFFS Bag Former.
The Core Difference: Where Product Meets the Bag
Both former types do the same job: they turn flat film into a tube. The difference is in how product fills the bag.
Collar-type: Product drops from the weigher or filler through the forming tube and falls freely into the bag by gravity. Fast, reliable, and universal for dry products.
Trunk-style: The forming tube is extended downward into the bag before filling. Product is delivered near the bag bottom, keeping the upper seal zone completely clear of the product flow. This is critical for powders and liquids, where even a small amount of product contaminating the seal zone causes seal failures.
| Collar-Type | Trunk-Style | |
| Product delivery | Top of bag — free fall by gravity | Near bag bottom — via extended tube |
| Seal contamination risk | Low for dry products | Near-zero — by design |
| Primary application | Granules, dry solids, snacks | Powders, liquids, pastes |
| Film width range | 35mm – 800mm | 35mm – 800mm |
| Bag styles | All standard formats | 3-side seal, 4-side seal, stick packs |
| Teflon options | Outer for film; inner for dust | Inner coating is critical |
| MOQ | 1 piece | 1 piece |
When to Choose the Collar-Type Former
The collar-type is the right choice when your product is:
- Free-flowing granules — nuts, coffee beans, sugar, rice, seeds, candy, frozen vegetables, hardware fasteners
- Dry solid pieces — snacks, pet food, chocolate chips, cereal
- Any product that fills cleanly by gravity without generating fine particles that drift back up toward the seal
The collar-type is available in round, square, oval, gusseted, and quad-seal formats. It is compatible with all major VFFS machine brands and covers the full film width range from 35mm to 800mm.
Browse our VFFS Bag Former range — includes specifications, compatible machine models, and customization options.
When to Choose the Trunk-Style Former
The trunk-style is the right choice when your product is:
- Powder — flour, spices, protein powder, milk powder, pharmaceutical granules, chemical powders. Powders generate airborne particles during filling that drift up and contaminate the horizontal seal area.
- Liquid — sauces, oils, vinegar, beverages, creams, ketchup. Liquids splash on impact and coat the seal zone before the jaws close.
- Paste or gel — jams, toothpaste, adhesives, cosmetic creams. These adhere to the forming tube and require the extended tube to ensure complete discharge.
With inner Teflon coating, the trunk-style former consistently achieves product qualification rates above 99% in powder and liquid filling applications.
Browse our Trunk-Style Former page — includes specifications by film width, tube diameter, and coating options.
The Grey Zone: Products That Could Go Either Way
| Produto | Recommended | Reason |
| Fine salt or fine sugar | Trunk-style | Fine particle size creates airborne contamination risk similar to powder |
| Instant coffee granules | Collar-type | Granule size is large enough that free-fall filling is clean |
| Freeze-dried fruit/veg | Collar-type | Irregular but dry — collar handles well at moderate fill speed |
| Protein powder (fine) | Trunk-style | High surface area generates significant dust during filling |
| Liquid honey | Trunk-style | High viscosity; slow fill with extended tube prevents drip contamination |
| Solid chocolate chips | Collar-type | Free-flowing and non-dusty — standard collar is sufficient |
If you are unsure, send us your product type and filling speed. We can typically make a recommendation and provide the relevant forming set within 24 hours of receiving your machine specifications.
Film Compatibility: How It Affects Your Choice
Film type does not determine collar vs. trunk — that is product-driven. But it does affect the surface treatment you should specify:
- Transparent PE / CPP film — standard mirror-polish finish; inner Teflon on trunk-style to prevent static adhesion inside the tube
- Thin OPP or metalized film — outer Teflon coating on collar-type to reduce friction-induced tension
- Kraft paper / paper composite — sand-blasted finish option for controlled grip without slipping
- Aluminum foil composite — outer Teflon to prevent micro-scratching of the foil surface
Tell us your film type when you order. We specify the right surface treatment as part of the standard process — no additional charge for standard Teflon options.
How to Order: 5 Things to Have Ready
To get an accurate recommendation and quotation quickly, have these five data points ready:
- Your VFFS machine brand and model number
- Your target film width and thickness
- Your product type (granule / powder / liquid / paste)
- Your target bag style (pillow / 3-side seal / 4-side seal / gusseted)
- Your filling speed in bags per minute
With these five inputs, we confirm the right former type, recommend the appropriate Teflon coating, provide a dimensional drawing for your approval, and give you a lead time. Standard models are in stock for rapid dispatch; custom orders typically complete in 7–10 business days.
Ready to order or need a recommendation? Visit our VFFS Bag Former page for collar-type forming shoulders (granules, dry products), or our Trunk-Style Former page for powder and liquid applications. Both pages include standard specifications and a direct inquiry form. You can also contact our technical team directly — send us your machine model and film width, and we will get back to you within 24 hours with a recommendation and free drawing confirmation.