Caused by the long curing time, at this time, there are residues on the surface of the adhesive, but the adhesive still pops open, because it is not completely dry, the bonding process has ended, and the bonding force between the hot melt adhesive will be very small, and the glue is separated from the glue, resulting in failure to stick. It is recommended to replace the hot melt adhesive with a short curing time or increase the pressing time so that the hot melt adhesive is completely cured before stopping the pressing.