warp sizing operations

Management expectations from sizing operations of weaving mills

Sizing the warp is science versus art. Despite a high degree of sophistication in the chemical and physical sciences as the apply to textile sizing, and despite great strides in the development of mechanical, computer and electronic equipment and control for slashing, the process is not an exact science. Rather it is an art which relies on a mixture of science, technology, experience and experimentation

Prime Function---Sizing operation is to produce weavability in the warp.   This short description relates to a rather complex process to obtain the desired results.A very important point to make is that errors in warp sizing can have disastrous effect in the weaving room and in the finishing department and thus on the final product.

Fundamental Aspects. ---In order to obtain a good weavability, the yarn should be made capable of withstanding the forces during the weaving process without being damaged, or becoming (extremely) hairy. The elasticity of the sized yarn should be high enough and the flexibility of the yarn should be sufficient to with stand these forces and movements. The size plays an important part in obtaining these results; the principal actions of the sizing are 1. Protruding fibres should stick to the yarn body (decrease hairiness )2. Tying fibres so that they are fixed in the yarn body, in order to prevent protruding fibres being disrupted. 3.giving a size film on the circumference of the yarn body (protection of the yarn).4. making thin places stronger. 5. Making thick places (with relatively low twist) stronger. 6. To reduce electrostatic formation for synthetic or blended yarns.

Benefits of Sizing

·        It prevents the warp yarn breakage due to abrasion with neighboring yarns or with back rest, heald eye and reed.

·        It improves the yarn strength by 10 to 20%, although it is not the primary objective of sizing process.

Characteristics of Sized Yarn expected by management

·        Higher strength

·        Lower elongation

·        Higher bending rigidity

·        Higher abrasion resistance

·        Lower hairiness

·        Lower frictional resistance

·        Creep factor affecting elongation and elasticity of yarns

The performance of the yarn in weaving improves as the size add-on increases. The optimum add-on level is marked by very low level of warp breakage rate. However, if the size add-on is higher than the optimum level then warp breakage rate increases again largely due to the loss of elongation and increase in bending rigidity of the yarns.

The optimum level of size add-on will depend on the following factors:

·        Type of fibre

·        Type of size materials

·        Yarn spinning technology

·        Yarn count and twist

·        Level of hairiness in the yarn

·        Loom type and loom speed

Although add-on primarily influences the weaving performance, it is possible to have different weaving performances even at the same level of size add-on. This can happen due to differences in (a) Size penetration and (b) Size coating or encapsulation

Formula check list.

After meeting the requirements for a perfect size formula in terms of sizing efficiency, there are another considerations which must then be weighed. These considerations must be met by answering following questions

1.      Will the material be available in uniform grades? If not there will be trouble ahead when results vary from one batch to another.

2.      Will the material be available when needed and in sufficient quality?

3.      Will the cost of the material be prohibitive? The price of material is itself is not the whole consideration. A high-priced material size may be worth the difference in results when compared with cheaper formula which causes frequent loom stoppages or ruined cloth.

4.      Will the material be compatible with other materials being used?

Only after the above questions are answered can a sound decision be made regarding the selection of a size.

1.The various properties which can be readily compared by known test methods and definitely have an effect on weaveability of the yarn are 1. Abrasion resistance under tension (test both yarns against yarn and yarn against metal)

2.increase in tensile strength.

3.minimum loss in elasticity.

4. Flexibility

5. Smoothness of film

6. Shock resistance, ability to withstand repeated strains

7. Resistance to cutting of adjacent ends by knots and gouts.

8. Fibre laying

9. Film hardness.

10.Sensitivity to changes in relative humidity.

11. Resistance to shedding.

12. Film strength

13. Adhesion to yarns.

14. Residual elongation.

15. Reduction of friction

These tests can give only some indication of what to expect in the weave room an indication is better than nothing, and often the reason why a warp is running improperly can be determined by such tests

Evaluation of sizing in the weave room

1.      Production efficiency

2.      Loom stoppages from warp defects

3.      Cloth quality

4.      Cloth appearance and hand

5.      Shedding of size

6.      Shedding of lint .

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