Impact of high speed drafting/ high draft ratio on cots & aprons:

1. The surface speed of front top roller cot increases as a result it has to make more revolution per unit time (rpm) as a result cots relaxation time (Rt) gets reduced proportionately. Here resilience property along with low compression set values of a cot plays a vital role. A cot having poor resilience will not recover its original geometry within that time interval and it may have permanent deformation leading to quality detoriation.

2. For the same time period, the cot and aprons should handle more volume of fibres since the productivity is more. Here abrasion resistance, wear & tear property along with other physical properties of the cots and aprons plays an important role.

3. Due to increased surface speed, handling high volume of fibres chances of lapping will be high (especially while using softer cots) due to excess static charge generation on the cots surface. In this case rubber compound conductive properties, core conductivity plays an important role.

4. In case of high draft ratio, the load on the aprons will be very high. This is due to the fact that front roller cot will have to exert more pulling force to get the fibres out of apron nip since surface speed of aprons will be lesser and more static friction takes place between fibers and apron surface. This increases the wear and tear of drafting apron.

5. The drafting combination had a significant influence on fiber speed. Increasing the drafting ratio will results in higher fiber speeds.

Conclusion:

High speed drafting with increased draft ratio significantly affects the life of individual drafting zone components especially cots & aprons. Frequency of flexing of bottom aprons at nose bar, wear out on both inner/outer layers generally increases .Cots rubber compounds abrasion resistance, anti-lapping properties together with high resilience property plays a vital role in deciding definitive yarn quality with consistency even at increased drafting speed with high draft ratio.

About the Author:

B. Sujai is a Manager-Application Technology, Inarco Ltd.