Glue Flap Sizes and Types

Eugineo asks –

Is there a difference on the performance of the box if it’s used the normal, half extended or full extended glue flap?

Typically a normal glue flap running the full depth of the box body and 1-1/4 to 1-1/2 wide with 95 to 100 percent glue coverage creates a manufacturers joint sufficiently strong enough to hold the contents of the box.

Extended glue flaps are longer than normal flaps and usually extend 1-1/2 to 2 inches beyond the depth (body) and onto both the top and bottom closing flaps of the box.  Extended glue flaps are typically used on shorter (lower depth) boxes to provide more gluing surface for a stronger box, but may be used anytime a designer feels a stronger glue joint is needed.

On Half Extended glue flaps the glue flap it extended 1-1/2 to 2 inches beyond the depth (body) but only on one of the closing flaps of the box, usually the bottom flap.

It’s also very important to ensure the proper amount of glue is being applied to the flap. Certainly, insufficient glue application can cause a weak manufacturers joint and result in failure of the box. Over gluing uses more material than is necessary, can make a mess of the equipment as well as cause quality issues with the finished box. In some cases over application can also weaken the glue joint. If you have questions about application, your gluing equipment manufacturer or your glue supplier should be able to provide necessary and helpful information.

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3 Responses to “Glue Flap Sizes and Types”

  1. George A. Moretti Says:

    Is an outside glue lap stronger that an inside glue lap?

    George Moretti

    716-909-1177

    >

  2. Brett Kendall Says:

    I’ve often wondered if our industry still needs such wide glue tabs. The combination of closed, pressurized extrusion systems and verification tools like GlueChek means we’re no longer dripping glue under the press or causing squeeze-out: 1/4″ removed from the tab would save 6 square inches of customer-paid waste on a 2 foot sheet, box after box, run after run.

    Besides an uninterrupted glue bead, the most important performance aspect of glue tab performance is stopping and starting the glue on the right spot. Even a very small amount of unglued tab (at the top or bottom) is like the start of a rip and the whole thing pops open with a bit of duress on the box. I think that’s the true value of an extended tab.

    Related topic: I had always assumed that a full-width, split-panel glue tab would add to BCT by creating a sort of 5th corner on the box. Yes, small changes can get statistically lost given the variability in BCT numbers, but test results don’t show me any gain. Perhaps if I trend the numbers a bit longer…

  3. katimavik86 Says:

    I’ve often wondered if our industry still needs such wide glue tabs. The combination of closed, pressurized extrusion systems and verification tools like GlueChek means we’re no longer dripping glue under the press or causing squeeze-out: 1/4″ removed from the tab would save 6 square inches of customer-paid waste on a 2 foot sheet, box after box, run after run.

    Besides an uninterrupted glue bead, the most important performance aspect of glue tab performance is stopping and starting the glue on the right spot. Even a very small amount of unglued tab (at the top or bottom) is like the start of a rip and the whole thing pops open with a bit of duress on the box. I think that’s the true value of an extended tab.

    Related topic: I had always assumed that a full-width, split-panel glue tab would add to BCT by creating a sort of 5th corner on the box. Yes, small changes can get statistically lost given the variability in BCT numbers, but test results don’t show me any gain. Perhaps if I trend the numbers a bit longer…

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