Case Sealer Troubleshooting: Causes & Fixes

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Problems on this page:

Tape not cutting cleanly Flaps lift or tape does not stick Cases jam in the sealer Tape wrinkled or off centre Tape head does not dispense or the tape breaks Top flaps not folded before taping Tape legs too short or uneven Drive belts slipping or stopping

Tape not cutting cleanly

Hits OEE: Availability

Symptoms: Tape tails hang from the back of the case, the tape is not cut at all, or the cut edge is ragged and stringy.

Dull or chipped cut-off blade

Replace the blade and keep a spare on the line; a blunt blade drags the tape instead of cutting it.

Adhesive build-up on the blade

Clean the blade with the solvent the tape head maker recommends at every shift change.

Weak blade guard or knife spring

Replace the spring so the knife fires with full force when the case passes.

Tape tension set too low

Raise the tension on the tape roll brake until the tape stays tight against the blade.

Prevention: Blade change and cleaning on the shift checklist, with the date written on the tape head.

Flaps lift or tape does not stick

Hits OEE: Quality

Symptoms: Cases leave the sealer closed but the flaps spring open later, or the tape peels off on the pallet.

Tape not rated for the temperature

Use a tape rated for cold or warm storage if the cases are sealed or stored outside normal room temperature.

Dusty or recycled board

Switch to a tape with a more aggressive adhesive for high-recycled or dusty board.

Wipe-down rollers not pressing the tape

Set the wipe-down roller pressure so the tape is pressed firmly along the full length.

Overfilled cases pushing the flaps open

Check the fill height and the flap fold upstream so the flaps close flat before taping.

Prevention: A tape spec matched to board and storage temperature, checked when either changes.

Cases jam in the sealer

Hits OEE: Availability

Symptoms: Cases stop between the drive belts, twist, or get crushed at the tape head.

Side belts not set to the case width

Set the belt width for each case size and mark the settings on the frame.

Worn or glazed drive belts

Replace the belts as a pair so both sides grip the case evenly.

Cases out of square or bulging

Correct the erector or packer upstream so cases arrive square.

Top head set too low for the case

Reset the head height to the case and check the height stops.

Prevention: A size changeover sheet with belt width and head height for every case.

Tape wrinkled or off centre

Hits OEE: Quality

Symptoms: Tape runs to one side of the seam, folds over itself, or has creases that leave gaps.

Tape roll not aligned with the case centre

Centre the tape mandrel on the seam and lock it in place.

Worn or sticky tape rollers

Clean or replace the guide rollers so the tape runs flat.

Uneven tape tension

Adjust the roll brake so the tape feeds smoothly without snatching.

Case not centred between the belts

Check that both side belts run at the same speed and pressure.

Prevention: Tape path cleaning on the weekly round.

Tape head does not dispense or the tape breaks

Hits OEE: Availability

Symptoms: The tape is not picked up by the case, or it snaps before the case is fully sealed.

Tape not threaded correctly

Rethread the tape following the path printed on the head.

Front roller not returning

Free and lubricate the roller arm and replace a weak return spring.

Tape roll brake too tight

Reduce the brake until the tape pulls off the roll without stretching.

Damaged or old tape stock

Replace rolls that are crushed, dried out or stored in the cold.

Prevention: Operators trained to rethread the head, with the threading diagram fixed to the machine.

Top flaps not folded before taping

Hits OEE: Quality

Symptoms: A flap is caught under the tape, folded the wrong way, or left standing up.

Flap folder arms out of adjustment

Reset the minor and major flap folders for the case size.

Product standing above the case

Fix the fill height upstream so the flaps can close.

Folder timing wrong for the line speed

Adjust the folder timing when the speed is changed.

Board too stiff at the score line

Ask the box supplier to check the scoring on the flaps.

Prevention: Flap folder settings included in the size changeover sheet.

Tape legs too short or uneven

Hits OEE: Quality

Symptoms: The tape does not run far enough down the front or back of the case, so the seal is weak at the ends.

Tape head set for the wrong leg length

Adjust the leg length setting on the head for the case.

Knife firing too early

Check the knife trigger and the case sensing arm.

Case speed through the head too high

Match the belt speed to the head rating.

Worn applying roller

Replace the roller so the tape is pressed down the full leg.

Prevention: Leg length checked on the first case after every changeover.

Drive belts slipping or stopping

Hits OEE: Availability

Symptoms: Cases slow down in the sealer, the belts stall under heavy cases, or a belt motor trips.

Belt tension too low

Re-tension the belts to the maker setting.

Belt surface contaminated with tape adhesive

Clean the belts and fix the cause of loose tape reaching them.

Motor or gearbox overloaded

Check the case weight against the sealer rating and the motor current.

Worn belt pulleys

Replace pulleys with worn lagging or grooves.

Prevention: Belt tension and wear checked on the monthly PM.

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

Related equipment guides: case erector · case packer · palletizer · stretch wrapper · conveyor · strapping machine · print and apply labeller · tray former

Stop the same fault coming back

Recurring case sealer 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.

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