Definition, Objects and Techniques of Sizing

Last updated on August 18th, 2023 at 09:49 pm

Table of Contents

Sizing

Sizing is a complementary operation carried out on warps formed by spun yarns with insufficient tenacity or by continuous filament yarns with zero twists. In general, when sizing is necessary, the yarn beam is warped; therefore, all beams corresponding to the beams are fed, as soon as warping is completed, to the sizing machine where they are assembled. Sizing consists of impregnating the yarn with particular substances that form on the yarn surface a film to improve yarn smoothness and tenacity during the subsequent weaving stage.

We can say that the process of applying a protective adhesive coating upon the yarn surface is called sizing.

Objects of Sizing

To improve the weave ability of warp yarn.
To maintain good fabric quality by reducing hairiness, weakness, and increasing smoothness and the yarn’s strength.
To increase the tensile or breaking strength for cellulose yarn.
To increase the elasticity.
To remove the projecting fibre.
To reduce electrostatic formation for synthetic or blended yarn

Different Techniques of Sizing

Hot melt sizing.
Solvent sizing.
Foam sizing.
High-pressure sizing.
Electrostatic sizing.
Emulsion sizing.
Combined sizing.
Conventional sizing.

Sizing Machines

The sizing process consists of impregnating with the size the warp unwound from the warping beams, drying, separating the ends and beaming. Moreover, during the sizing process, the warp is marked for dividing it into pieces of predetermined length.

The main parts of a sizing machine are the creel for the accommodation of the warping beams; the framework and drive; the sizing unit consisting of a size box and immersion and squeezing rollers; the drying section where the excess moisture is removed from the size and pressed warp ends; the headstock. A particular device is also provided therein for additional treatment, i.e. emulsification and waxing of sized warp, and automatic instruments for checking the sizing process.

Depending upon the arrangement of the drying section, all sizing machines may be classified as follows:

Cylinder sizing machine – in which the warp is dried by contact with the hot surface of the cylinder;
Hot air sizing machine – in which drying is effected in chambers with hot air;
Combined sizing machine – in which the warp is dried by contact with the hot surface of the cylinders and bypassing through hot air chambers;
Special sizing machine – in which the warp is dried by electric heating, high-frequency currents, by infra-red rays etc.