Bag Former Skew? Master the 2mm "Life Line" for Smooth Film Flow

Bag Former Skew? Master the 2mm "Life Line"

Make Film Flow as Smooth as Silk

Cover: the 2mm gap between jaws and former decides everything

Changed to a new film width, swapped in a new former, and as soon as the film starts feeding it looks crooked and drags like a saw. The technician circles the machine for 30 minutes before realizing the gap between the seal jaws and the former is off.

Today we cover a millimeter-precise critical number: the seal jaws should be 2mm from the bag former. That 2mm gap is the "life line" of smooth film feeding.

1. Why Exactly 2mm?

“In normal operation, simply adjust the relative position of the left/right seal jaws and the former according to film size; generally, a gap of about 2mm is recommended.”
— VFFS instruction manual — middle-seal adjustment

2mm is not arbitrary. Film passes through the former and is then clamped by the seal jaws for the longitudinal seal. Too close and the jaws squeeze the film too hard — drag spikes, wrinkles form, even tears. Too far and the seal pressure is insufficient — seal pattern blurs, bags leak and burst.

•  Gap <2mm: excessive film drag → wrinkles and poor feed

•  Gap ≈2mm: smooth feed, flat and airtight seal

•  Gap >2mm: seal misalignment → weak, leaky seam

Fig. 1: Three gap states compared (from the manual, middle-seal adjustment)

2. The 4-Step Adjustment

The manual specifies exactly four actions:

•  Step 1: loosen lock handle A to release the jaws;

•  Step 2: turn the adjustment knob CW or CCW to change the jaw-to-former gap;

•  Step 3: until the left and right jaws are 2mm from the former;

•  Step 4: tighten handle A so production vibration cannot shift the gap.

Fig. 2: 4-step former & jaw gap adjustment (from the manual, middle-seal adjustment)

✔  The seal jaws are carefully adjusted and tested at the factory; normally no adjustment is needed. Re-check only after changing the former size (film width).

3. Former Change: Size Must Match First

The former is not universal. The manual states: when changing packaging width is needed, simply remove the former assembly and install the corresponding size.

⚠  The former size must match the film width. Wrong size means the forming path itself is wrong — no matter how precisely you set the 2mm gap, the film will still feed crooked.

4. Cross-Check: Film Tension Too

Even with the gap correct, if feeding is still rough, check film tension. The manual notes: if tension is uneven as the film passes through the former, feeding will be rough — adjust it before starting the machine.

Adjustment: loosen the left/right adjustable handles, rotate the swing bar forward/back to change the tension roller's relative position to the former, achieving even film tension at entry.

Final Thoughts

Next time the former goes in crooked, measure that gap first — 2mm; not one thread more or less.

Next: how the pressure sponge's position decides whether your bags come out puffed or flat.

Call to Action & Series Note

Still fighting crooked film feed?    Send us your film width and former size — our engineers will confirm the 2mm gap setup. Or reply with keyword "manual" to download the VFFS Instruction Manual (PDF).