Bag‑closing machines are core equipment for sealing jute bags, PP woven bags, fertilizer‑feed sacks, filter bags and big‑bags. Long‑hour continuous operation will bring thread‑breaking, skipped stitches, feeding failure and other issues, which cause production downtime and bag‑sealing quality risks. Below we sort out frequent failures, root‑cause analysis, practical fixes and standardized maintenance suggestions for PACKSTAR series bag‑closing sewing machines.
1. Common Troubles & Troubleshooting
|
Symptom |
Possible Causes |
Solutions |
|
Thread breaking frequently |
1. Wrong threading path; thread tension is too tight 2. Burrs on needle, looper/hook, thread guide 3. Mismatched needle‑thread‑bag material 4. Looper‑needle timing offset |
1. Re‑thread strictly following machine manual; release tension dial moderately 2. Replace bent/blunt needle; polish or change burred looper hook 3. Match heavy‑gauge needle for thick woven bags; adopt high‑strength polyester sewing thread 4. Recalibrate needle‑looper timing by professional technician |
|
Skipped stitches / loose stitch loops |
1. Needle installed reversely, bent or worn out 2. Unbalanced tension between needle thread & looper thread 3. Improper clearance between needle and looper 4. Presser foot pressure too light |
1. Install new needle in correct orientation 2. Adjust tension, make stitch knot lock in middle of bag fabric 3. Fine‑tune looper gap (0.1‑0.3 mm standard) 4. Increase presser‑foot pressure appropriately |
|
Broken needles |
1. Bent needle; needle collides with looper / throat plate 2. Thin needle for extra‑thick multi‑layer bag material 3. Operator pulls bag forcibly faster than machine feeding speed 4. Foreign hard impurities mixed inside bags |
1. Fit correct heavy‑duty needle for bag thickness; check needle installation depth 2. Train operators: let feed dogs pull bags automatically, do not drag bags manually 3. Remove hard debris before feeding bags; inspect needle‑looper clearance again |
|
Poor feeding, crooked sewing, uneven stitch length |
1. Feed dog teeth worn or height abnormal 2. Presser foot pressure too high or too low 3. Bag‑guide position offset; conveyor‑head speed mismatch for inline‑model |
1. Adjust feed‑dog height (0.8‑1.2 mm above needle plate); replace worn feed dogs 2. Tune presser‑foot spring pressure: heavier for thin bags, lighter for thick multi‑ply bags 3. Realign bag guide; synchronize sewing‑head speed with conveyor speed for automatic lines |
|
Automatic thread trimmer fails (no cut / ragged cut) |
1. Moving/fixed cutting blades worn or chipped 2. Thread residue jammed between cutter blades 3. Cutter assembly position shifted |
1. Clean lint and thread scraps on cutters 2. Re‑align cutter overlap position; replace blunt cutters as spare parts |
|
Abnormal noise & mechanical jamming |
1. Lack of lubrication; thread/lint buildup inside mechanism 2. Belt loose or gear wear; foreign thread wound on rotating shaft |
1. Stop power supply first; clean accumulated lint and tangled threads 2. Lubricate gears, shafts and linkages; tighten or replace worn transmission belts |
2. Routine Maintenance Tips
Proper daily, weekly and periodic maintenance greatly extends machine service life and minimizes unexpected breakdowns, suitable for PACKSTAR small‑bag sewing machines, big‑bag sewing machines and high‑speed bag‑closing systems.
Daily Maintenance (Each shift)
- Cut off power before cleaning. Blow or brush away lint, woven‑bag dust and thread scraps from looper, feed dog, needle plate and thread‑passing parts every shift.
- Add specified sewing machine oil to all marked oil holes before startup. Run machine idle for 30 seconds to spread oil evenly before formal sewing.
- Quick visual check: needle condition, thread path, presser‑foot fastening, no loose screws.
- Check thread quality; avoid low‑strength or uneven thick‑thin thread which easily causes breakage.
Weekly Maintenance
- Full lubrication for gear sets, rocker arm assemblies and driving linkages.
- Inspect wear parts: needle, looper hook, feed dog, presser foot, cutter blades; prepare genuine PACKSTAR spare‑parts for replacement.
- Check belt tension, screw tightness of sewing‑head mounting base.
- For conveyor‑integrated bag‑closing lines: clean conveyor surface and check sensor sensitivity.
Quarterly Maintenance
- Comprehensive disassembly‑cleaning for hook‑looper assembly, remove aged oil and dirt.
- Check motor carbon brushes; replace brushes when heavily worn.
- Re‑calibrate needle‑looper timing, stitch length, presser‑foot pressure and cutter position.
- Tighten all electrical wiring terminals, inspect cable insulation, ensure good grounding for safety.
Long‑term shutdown preservation
- If machine will be idle for more than 7 days:
- Thoroughly clean all dust and thread waste.
- Apply thin protective oil on metal moving surfaces to prevent rust.
- Remove needle; cover whole machine with dust‑proof cover; store in dry, dust‑free workshop environment.
3. Operation Safety & Best‑practice Reminders
Always power‑off before doing cleaning, lubrication or adjustment work to prevent accidental startup injury.
Match needle, thread and stitch parameters to your bag material: PP woven sack, jute bag, filter bag and big‑bag require different needle specifications.
Do not pull or drag bags manually during sewing; let machine feed material by feed dogs. Forced pulling will bend needle, break thread and damage internal mechanism.
Keep key wear‑parts in stock: needles, loopers, cutters, feed dogs. Use original PACKSTAR spare parts for best compatibility.
If repeated faults persist after basic troubleshooting, please contact Deko Corporation technical support rather than disassembling core timing components blindly.
Contact us:
Email: dekoco@vip.163.com｜sales@chinapackstar.com
WhatsApp/WeChat: 0086 13991289750/ 0086 18192599526
