The automatic bagger is installed and day one does not run: bags will not open, seals come out brittle, jams three times an hour. The instinct is to adjust the machine, but the problem usually sits in the bag itself — gauge, anti-block additive and roll geometry that do not match the machine, so no amount of parameter tuning helps.
This guide covers four things: which bag type each machine family accepts, how to choose between roll film and flat bags, the seven causes of jams, and a trial-run checklist you can send straight to a supplier.
1. First Confirm What the Machine Actually Feeds On
Changing bag type on the same machine usually means changing vacuum cups, guides or sealing jaws. Settle the bag type before buying the machine, not after it lands on the floor.
| Machine type | Usual bag type | Key parameters |
|---|---|---|
| Automatic bagger | Roll bags, wicket bags | Bag width range, opening direction, suction position |
| Flow wrapper | Laminated roll film | Film width, roll diameter, eye mark |
| Vertical form-fill-seal | Roll film | Film width, seal temperature, film-feed accuracy |
| Manual or semi-automatic | Flat bags | Gauge, opening style, print position |
2. Roll Film or Flat Bags: Three Tests
- Volume: above a few thousand pieces per shift, continuous roll feed saves labour; for small runs and frequent style changes, flat bags switch faster without stopping to change rolls.
- Size variation: one size per style is easier to manage with flat bags sorted by spec; a single stable size over months favours roll film on unit cost.
- Printing: roll film is positioned by an eye mark, so the artwork must leave room for it; flat bags need no mark, but the mouth wrinkles easily and artwork needs a safe margin from the seal.
3. Gauge, Friction and Opening Behaviour
Garment bags typically run 25–50 μm. Thinner saves material but makes suction unstable and bags tear; thicker looks crisper but demands higher seal temperature and machine load, which costs speed.
- Friction: a dynamic coefficient around 0.2–0.4 is usually stable. Too low and the web slips and tracks off the rollers; too high and bags will not open or stack squarely.
- Anti-block and slip agents: too little and bags block together; too much and print adhesion drops along with seal strength. It is a trade-off inside one formulation.
- Static and humidity: a dry winter floor makes bags refuse to pick or pick two at once. Holding the room at 50–60% relative humidity stabilises the process considerably.
- Venting: perforated bags lose suction, so you need larger cups or a different pickup position, or the machine simply misses.
4. The Roll Geometry You Must Specify
- Core diameter: commonly 76 mm (3 inch), sometimes 38 mm. Get this wrong and the roll will not mount at all.
- Roll diameter and weight: limited by the unwinder. Oversized rolls snap the film or send tension out of control, and tracking drifts as the run goes on.
- Splices per roll: put it in the contract. Automatic lines are unforgiving about tape splices, and above the agreed count the roll should be replaced.
- Eye marks: pitch, position and contrast must match the photocell. If artwork covers the mark, the knife simply has nothing to register on.
5. Seven Causes of Jams and Weak Seals
- The bag is too thin, deforms under suction and enters the guide out of line.
- Blocked mouths: insufficient anti-block, or bags stored in damp air that absorbed moisture.
- Cup size does not match bag width, so it grabs off-centre or not at all.
- Unstable web tension makes the film track off and the knife cut into the artwork.
- Seal temperature or pressure is short, the laminate never melts through, and the seam peels open.
- Artwork runs into the seal zone: ink over the sealing area cuts seam strength outright.
- Air too dry: static makes the machine pick two bags, and two bags jam the guide.
6. Trial-Run Checklist: Get the Sample Right First Time
| Information needed | Why it matters |
|---|---|
| Machine model and bag width range | Sets the usable size window for the bag |
| Cup size and count | Sets pickup position and any reinforced area |
| Seal method and temperature | Drives the laminate structure and sealant layer |
| Line speed (pieces per minute) | Sets gauge, tension and maximum roll weight |
| Trial quantity | Two rolls per spec, at least 200 m each |
| Approval cycle | Three to seven days to a production sample after the trial, leaving room for revisions |
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Installing an automatic packaging line and need bags that actually run? Send the machine model, bag width, cup details and line speed; we ship two trial rolls first and fix the bulk spec only once it runs clean. Sampling 3–7 days, bulk 10–25 days.
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