Bag Closing Machine Troubleshooting: Causes & Fixes

Not your exact symptom?

Describe it in the symptom finder and search the whole directory.

Problems on this page:

Skipped stitches Thread breaking Bag tops not fed straight Stitch chain unravelling Needles breaking Heat sealed closure not bonding Bag top folding badly Thread cutter not cutting Sewing head running hot or noisy

Skipped stitches

Hits OEE: Quality

Symptoms: Gaps appear in the stitch line and product can leak from the bag top.

Needle bent, blunt or fitted the wrong way

Replace the needle and fit it with the groove facing the way the maker shows.

Thread tension wrong

Set the thread tension for the thread and bag material.

Looper timing off

Check the timing between needle and looper as the maker describes.

Bag material too thick for the head

Check the head and needle are suited to the bag material.

Prevention: Stitch quality checked on bags at start-up and after each needle change.

Thread breaking

Hits OEE: Availability

Symptoms: The thread snaps during sewing and the line stops.

Tension too high

Reduce the thread tension.

Burr on the needle, guides or throat plate

Find and polish or replace the part with the burr.

Thread quality poor or wrong size

Use the thread specified for the head.

Thread path threaded wrongly

Rethread following the threading diagram on the head.

Prevention: Thread breaks recorded by shift to spot a pattern.

Bag tops not fed straight

Hits OEE: Quality

Symptoms: The stitch line runs off the bag top or the top is caught crooked.

Bag guides set for another bag size

Set the infeed guides for the bag in use.

Conveyor and sewing head speeds not matched

Match the conveyor speed to the sewing speed.

Bag top folded or creased before the head

Check the top forming and the operator presentation of the bag.

Bags filled unevenly and leaning

Check the filler and bag settling before closing.

Prevention: Bag guides on the changeover checklist.

Stitch chain unravelling

Hits OEE: Quality

Symptoms: The chain stitch pulls out from the end of the seam.

Thread chain cut too short

Leave a longer chain tail when cutting.

Thread tension too low

Increase tension to the setting for the bag.

Stitch length too long

Shorten the stitch length.

Tape or binding missing on bags that need it

Use the tape the closure specification calls for.

Prevention: Seam pull test on sample bags.

Needles breaking

Hits OEE: Availability

Symptoms: Needles break often and need to be changed during production.

Needle hitting a hard object in the bag top

Keep product out of the bag top area before sewing.

Needle too thin for the material

Use a heavier needle for thick bags.

Bag pulled while the needle is down

Match conveyor and head speeds.

Needle bar loose

Check the needle bar and clamp.

Prevention: Needle use recorded per shift.

Heat sealed closure not bonding

Hits OEE: Quality

Symptoms: On bags closed with a heat activated tape or pinch closure, the closure opens or peels.

Heater temperature too low

Check the heater temperature against the bag maker specification.

Conveyor too fast for the heater

Slow the conveyor or raise the heat within the specification.

Pressure rollers worn or set wrong

Check the pressure rollers.

Adhesive on the bag damaged or old

Check bag storage and age.

Prevention: Closure peel checked on sample bags.

Bag top folding badly

Hits OEE: Quality

Symptoms: Folded tops are uneven, so the stitching or tape misses part of the top.

Folder plates set wrong

Set the folder for the bag size.

Bag top too short above the product

Check the fill height and bag length.

Bag material stiff or curled

Check bag storage conditions.

Folding rollers worn

Replace worn rollers.

Prevention: Fold quality checked at start-up.

Thread cutter not cutting

Hits OEE: Availability

Symptoms: The thread chain is not cut between bags, linking bags together.

Cutter blade blunt

Replace or sharpen the cutter blade.

Cutter trigger sensor misaligned

Adjust the sensor that fires the cutter.

Air pressure low to the cutter

Check the air supply.

Cutter timing wrong for the speed

Set the cutter timing.

Prevention: Cutter blade changed on a fixed schedule.

Sewing head running hot or noisy

Hits OEE: Availability

Symptoms: The sewing head gets hot or louder than usual.

Lubrication missing

Oil the head as the maker specifies, often daily on busy lines.

Dust and fibres packed in the head

Blow out and clean the head regularly.

Worn parts in the head

Have the head serviced.

Belt tension wrong

Check the drive belt.

Prevention: Head lubrication on the daily checklist.

Guidance only. Always follow lockout/tagout and your site's safe-work procedures, and verify against OEM manuals before acting.

Related equipment guides: bagging machine · big bag filler · palletizer · checkweigher · metal detector · impulse heat sealer

Stop the same fault coming back

Recurring bag closing machine stops usually trace to a cause you cannot see by hand. The partner we recommend is Fabrico: it tracks OEE and downtime live from PLCs, IoT sensors or AI cameras; where cameras are fitted, the video of a stop sits next to its machine data so the cause can be reviewed; and a technician opens the work order from the stop in the same system. Data is hosted in the AWS EU region, and Fabrico and the company behind it hold ISO/IEC 27001, ISO/IEC 20000-1 and ISO 9001.

Book a Fabrico demo

The directory stays free.

Methods that cut recurring stops: the six big losses · root cause analysis · preventive vs predictive maintenance · TPM · SMED & changeover