Sizing | The Functions of the Sizing Operation | Sizing Variables

Sizing is a complementary operation which is carried out on warps formed by spun yarns with insufficient tenacity or by continuous filament yarns with zero twist. In general, when sizing is necessary, the yarn is beam 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 which form on the yarn surface a film with the aim of improving yarn smoothness and tenacity during the subsequent weaving stage

 

Thanks to its improved tenacity and elasticity, the yarn can stand without problems the tensions and the rubbing caused by weaving.

The functions of the sizing operation are:-
1. To lay in the protruding fibers in the body of the yarn and to cover weak places by encapsulating the yarn by a protective coating of the size film. The thickness of the size film coating should be optimized. Too thick a coating will be susceptible to easy size shed-off on the loom.

2. To increase the strength of the spun warp yarn without affecting its extensibility. This is achieved by allowing the penetration of the size into the yarn. The size in the yarn matrix will tend to bind all the fibers together. The increase in strength due to sizing is normally expected to be about 10 to 15% with respect to the strength of the unsized yarn. Excessive penetration of the size liquid into the core of the yarn is not desirable because it affects the flexibility of the yarn.

3. To make a weaver’s beam with the exact number of warp threads ready for weaving.

Sizing variables:
A good sizing depends on various factors. During sizing the following variables should be checked and controlled where necessary:

1. Viscosity of the size solution.·
2. Sizing machine speed.·
3. Size add-on levels.·
4. Concentration of the size mixture.
5. Volume of the size box.·
6. Threading arrangements.·
7. Condition of squeeze rolls.
8. Squeezing pressure.·
9. Hardness of squeeze rolls.
10. Diameter of squeeze rolls.
11. Number of size boxes.·
12. Yarn count and size box warp density per unit space.