Why am I experiencing wavy selvages?
Wavy selvages normally appear only after the cloth has conditioned for several hours or even days after having been pre-shrunk.
In most cases, the problem is caused by moisture differential between the cloth edges and the body of the cloth. A typical reason for this differential moisture is excessive moisture pick up by the cloth edges due to over spray during dampening of the goods prior to entry into the rubber belt. The cloth edges may pick up extra moisture from skyer rolls if spray pattern is too wide for the cloth.
Under spray can also cause this problem if cloth edges are dryer, relative to the body of the cloth when it enters the rubber belt unit.
Sometimes, when belt tension has not been increased during belt grinding, excessive curl of the belt edges will result in the edges being ground thinner than the body of the rubber belt. Thin belt edges will carry more rubber belt cooling water, which will be absorbed by the cloth edges.
Improperly adjusted, or poorly operating water removal rolls may also allow more cooling water to remain on the belt edges and can result in wavy selvages.
Rubber belts that are too narrow for the cloth being processed may develop wavy selvages. The rubber belt ideally should be 8 inches (200 mm) wider than the widest cloth to be processed.
Using insufficient temperature of the steam heated rubber belt cylinder can sometimes result in wavy selvages.
Insufficient palmer cylinder temperature can result in cloth edges leaving the palmer with more moisture than the body of the cloth Occasionally a wavy selvage on only one side or on both sides of the cloth can sometimes be traced to a worn or improperly operating pad used prior to dry cans in the process prior to compressive pre-shrinking.
There is occasionally a tendency for liquid squeezed from the cloth at the pad to follow the diagonal twill pattern to one side of the goods resulting in that side of the goods retaining greater moisture. Even after partial drying on heated cans, moisture on the one side may be higher.
Rolls of heavyweight denim taken from the pad/dry can finishing range with 7% or more residual moisture, if not passed through the compressive shrinking machine within 4 hours or less may sometimes have dryer edges at the time the goods is being pre-shrunk and this can result in wavy selvages.
Standing rolls of pre-shrunk goods on end will often result in wavy selvages.