Best Practices to Avoid Folder-Gluer Rejects

folder gluer machines for commercial

Best Practices to Avoid Folder-Gluer Rejects

Folding and gluing machines create hundreds upon hundreds of packaging every hour they’re operating. And it’s in the best interest of manufacturers to ensure that as few of these as possible contain defects.

It is critical to avoid creating rejects in order to avoid extra costs and wasted time. Here are the best practices of folding and gluing processes in order to avoid defects in the packaging you manufacture.

Creating an Accurate Design

It is important to consider the folding and gluing process during the design stage, along with the other considerations regarding design. This is because the process is three-dimensional. Any mistakes in the design can cause defects to occur more often during the manufacturing process.

Ensure that all measurements in the design are accurate. This becomes more important the more complicated the shape of the packaging is.

The score lines are another important part of the design. These are the lines along which the paper or carton will be folded. These have to be as accurately placed as possible to avoid an uneven shape.

Coating before Running Stock Through the Folder-Gluer

Coating helps prevent scuff and protects the print during the gluing and folding process. You can use either a cured UV or aqueous coating and apply it inline or offline. Even once coated, you should avoid having the stock get in contact with guides, bars, and other static tooling.

If you choose to run stock through the folder-gluer, do so after the ink has dried completely. Wet ink will easily scuff and offset from tracking on the machine.

Avoid Coating Glue Flaps

Coating protects the stock. However, it can also prevent glue from properly penetrating the paper stock and creating a proper bond. This is why it’s important to avoid any type of coating on the glue flaps.

There are technologies, like plasma treating, that allow operators to treat the coating so the glue will penetrate. However, how well this works also depends on the coating being applied properly. This makes it less efficient than avoiding coating the glue flaps as one defect in the coating means another defect in the gluing.

Preparing Metallic Surfaces for Gluing

Without proper treatment, stock that includes hot foil, cold foil, or a metallic board will not glue properly. During the die cutting process, perforations can be added to the gluing area. This allows the glue to penetrate the metallic surface.

You can also use a combination of hot melt and cold glue. The hot melt can help the cold glue by giving it dots which it can use to bond the carton together.

Use Quality Paper Stock and Carton Board

The folding and gluing process is affected by the quality of the paper stock or carton board. The higher the quality, the smoother it runs through the folding-gluing process.

However, this also costs more. Manufacturers have to balance the cost and the quality in order to produce the least amount of rejected packaging while also not paying too much for a high-quality stock. Larger runs might need a better quality stock, so consider this as well.

The Right Scoring and Folding Process for the Stock

There are many different types of packaging materials like paperboard and corrugated cardboard. The best process differs depending on what is being used. Heavier boards should be scored in the same direction as the paper grain. This results in it being folded better. Lighter stock should be scored from the opposite side.

The best way to determine the best process for what you’re using is to simply ask your provider. Typically, die makers have comprehensive charts that can tell you which way of scoring will result in the best folds for the stock you’re using.

New, Clean Belts

Scuffing can also be caused by the belts, particularly with the feeder section where they accelerate to speeds greater than 22 mph within seconds. This can create a burn-out effect on the print. Using newer, cleaner belts and allowing the paper stock or carton to come into contact with as much of the surface of the belt as possible will reduce the effect.

Folding and Gluing Machines for Optimal Production and Less Rejects

SBL Machinery has been operating since 1968 and has since become a leading folding and gluing machine manufacturer. We’ll equip your operators with the means to optimal production rates and less rejected packaging products.

Get in touch with us by emailing us at or call us at +886 2 2680-2199.

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