Problems, Common Causes & Solutions
In this three-part series, Technician Mike Frosh has compiled a list of nine problems he often encounters during service calls and their common causes. This entry focuses on three problems: overuse of glue, double-bonding, and over-coverage.
Problem: Overuse of Glue
This presents as too much glue on the wheel or too heavy of a pattern applied on the box tab.
Common cause: Most often, the glue shoe metering plate is set too far from the wheel.
Solution: Remove the glue shoe and reset the metering plate.
You might also read: How to Set the Metering Plate
Note: If the glue is smearing, then widen the gap between the wheels by adjusting the Nip Adjustment (see below)
Connected to the previous problem, double-bonding (or wheel contamination) presents with the transfer of glue onto the wheel opposite the side running a glue pattern.
Common cause: The gap between the Upper and Lower Glue Wheel is too narrow. This crushes the glue tab and squeezes glue toward the edges of the glue wheel.
Solution: Correct the Nip Adjustment to widen the gap between the Upper and Lowe Glue Wheel. This is also a good time to ensure the metering plate in the shoe hasn’t been adjusted out too far.
You might also read: Setting the Mechanical Nip Adjustment.
Note: When setting the Nip Adjustment, always when the machine is not under power and following your plant’s safety guidelines, use a clean sample of the glue tab. When setting this by hand, a slight drag of the tab as it passes between the wheels is best. If the gap is too wide, the box falls away from the wheel. If it’s too tight, it can crush and even skew the box.
Over-coverage of glue occurs when the supply of glue on the shoe exceeds the reservoirs we’ve machined onto the wheels (i.e. the pattern).
Common cause: A dirty or worn Glue Shoe.
Solution: Remove the Glue Shoe and clean. This includes removing all dried glue or buildup from the working surfaces. If the shoe is worn, jagged, or uneven, send it back to Gartech for a redress.