company news about TROUBLESHOOTING BOARD CRUSH-Industry News

TROUBLESHOOTING BOARD CRUSH

SUCCESSFUL DIAGNOSIS AND RESOLUTION REQUIRE A
METHODICAL APPROACH.

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BY WAYNE PORELL
HARPERLOVE
 

Caliper loss and crushed board can lead to a wide range of issues within a customer's

packaging operations and supply chain. Many of today's customers use automatic box set-

up equipment in their packaging lines and variations in board caliper can cause throughput

issues and jams. Caliper loss can also lead to false scores, poor print quality, unreadable bar

codes, loss of compression and ultimately potential box failures in the field. There are many potential causes of caliper loss, so successful diagnosis and resolution require a methodical approach. Start by identifving any changes that were made immediatelv prior to the appearance of the issue. It could be as simple as a repair or adjustment not properly completed, or a raw material change. The most recent change could quickly lead you to the root cause of the problem.

If you cannot identify a recent change that is causing the caliper loss, then you should proceed through a thorough review of the machine, starting at the wet end:

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• Add the caliper of both liners to the flute height of the corrugator rolls. This gives you the theoretical caliper for the combined board.

• Measure the caliper of samples of both liners cut from various positions across the web to check for consistency.

• Cut samples of the singleface board on the operator side, centre and drive side of the machine. Inconsistencies here may indicate a worn or out-of-spec corrugator roll.

• Cut samples of the doubleback liner on the operator side, centre and drive side, and measure the calipers of these samples combined with the singleface samples. These combinations will provide the baseline caliper for the combined board and determine.

if variations in the paper are causing the variations in the board caliper.

• Confirm that the medium preconditioner is turning at the correct speed and that the steam shower is operating properly. Problems with this equipment can lead to flute fractures.

• Check the pressure and corrugator rolls to confirm parallel. Too much corrugator roll loading pressure will cause crush.

• Belt tracking issues Measure the gap between the glue roll and the bottom corrugator roll. Cut and measure a sample of the combined board before the web guides to check if the incline belts or a roll/wheel on the bridge are causing crush.

• Cut and measure a sample after the web quides prior to entering the doubleback glue station. Some parts of the web quides can wear and cause crush issues.

• Cut a sample after the glue station again from all three areas across the web. Crush here can be caused by a) a rider roll or contact bar that is out of parallel, b) if the T.I.R. is out of range, or c) a bad bearing in one of the rolls.

or contact bar that is out of parallel, b) if the T.I.R. is out of range, or c) a bad bearing in one of the rolls. Also check the glue roll for the same issues.

• The hot plate section can crush the board with several of its components. Cut samples directly after the combined board exits the head pulley. If you find crush exiting the head pulley, you will then need to cut samples from the outer edges of the web in the hot plates. If the hot plates have a high leading edge in the paper travel direction, this can cause crush as well as delamination issues. Also, look for dried starch on the hot plates which can crush the board.

• If the plant is using weight rolls, worn bearings can allow the roll to bounce and crush the board. If the weight roll arm gets hung up on one side, this puts all the weight of the roll on one side of the sheet instead evenly distributing it.

• Uneven hot plates Many customers use automatic box set-up equipment in their packaging lines and variations in board caliper can cause throughput issues and jams.

• Fractured flutes  If the plant is using shoes and one of the shoes malfunctions and stays down, it will crush the board. This is why it is important to keep the moving parts of the shoes clean and working correctly. Measure the caliper of the top corrugator belt across the width of the machine and at various positions on the web. Caliper variations in the belt can cause caliper variations in the board. Variations in belt caliper can also lead to a weaker bond corresponding to the thin areas of the belt because of inadequate pressure to hold the web and bottom liner together. Evidence of this problem will show up as spotty glue lines on a soak test. The traction section can cause the crush issues if the ballast rolls have bad bearings or the arms holding the rolls get hung up. This is similar to the issues with the weight rolls. The knife can crush the combined board if the entrance rolls or exit rolls are out of parallel or have too much loading oressure.

• No-crush wheels can crush the board if they are installed in the wrong direction. The fins in the middle of the wheels must be able to flex. If they are improperly installed and not able to flex, they can cause crush issues.

• Finally, the stacker can cause crush if too much pressure is put on the no-crush wheels entering the stacker bed. Identifying the causes of crushed board can sometimes be difficult and time- consuming, but a thorough and methodical approach will help you pinpoint the root causes and will reduce customer issues and returns.