Direct sizing is a one step process and can also be referred to as beam to beam sizing. For cases where the warp density is high, the warp sheet is separated into two or three sheets, depending on the number of size boxes, before entering the size bath to ensure more uniform and better penetration and encapsulation of the size. It is recommended by some, to split the warp sheet after exiting the size bath by means of a splitting rod to prevent the groups of ends from becoming displaced, which may cause a stripe effect in the warp. This is known as wet splitting and is mainly due to preventing size bridges from forming. After drying, the sheets are separated by a bursting rod and again by leasing, or splitting, rods before entering the comb area where each individual end is separated and wound on the beam. an ideally sized warp is one in which individual ends are separated from their adjacent ends in the correct order and uniformly spaced across the width of the warp
There are Two Methods of Direct Sizing in a One Step Process
The differences between the two methods include the number of beams going into the process and the method in which the beams were prepared by the warping process. After indirect warping one complete beam, containing all the required number of ends, it is possible to size this beam and produce one sized loom beam. This method, sometimes referred to as beam to beam sizing.
Indirect Sizing is a two step process, involving sizing and beaming. This process, frequently called single end sizing, is generally used for filament yarns. The phrase single end sizing originated because the yarns are sized with equal space, two or three yarn diameters, between them. This meant there is no need to split the yarns after the drying process because the size is encapsulated around each individual yarn. Since there is no cohesion between the yarn ends there will be no formation of size bridges between adjacent yarns .
A size bridge is an accumulation of size that joins two adjacent yarns. The two yarns once separated will break apart the size bridge, exposing unsized areas on the yarns. This causes two effects: increased hairiness of the yarns, in spun yarns only, and hard size from the size bridge which can cause end breaks or defects if woven into the fabric.
Hot Melt Sizing
The technology of hot melt sizing was patented by Burlington Industries and was developed, under agreement, by West Point Foundry and Machine Company . This 1960’s technology was one of the first sizing technologies to provide yarn encapsulation. However, this technology is not widely used today as a sizing technique.
Hot melt sizing is an integration of the warping and sizing processes. It is quite different from that of other traditional warp sizing processes. There are no size boxes or drying sections present in this process. The process begins while the yarns are still in the warping process.A rotating, heated applicator roll, located between the warper creel and the warper, applies a molten, 100% active size to the yarn. The warp yarn is drawn over the grooves of the roll which separate the ends during the size application. The size, in the form of a solid block touching the surface of the roll, begins to melt into the grooves as the heated roll turns and the yarn passes through. The yarn, traveling at a much higher rate of surface speed than the applicator roll, has time to pick up the molten size and which then cools around the yarn before the yarn is wound onto the warper.
Winder sizing is the process that most people in the textile industry previously called single end sizing since one yarn end is sized at a time. The sizing winder is used to convert a single unsized, wound package into a sized wound package. More modern sizing winder machines have an individual motor driving system which controls each spindle and yarn pick up device. This allows for greater efficiencies and less downtime. Just like any other standard sizing process, the machine consists of a supply package holder, tensioning device, size application zone, drying zone, and winding zone for the delivery sized package.