Abstract:

Now-a-days, in normal ring spinning system to increase the productivity two key factors which determine the increased productivity are spindle speeds of ring frame and end breakage rate. Modern ring frames can run at high spindle speeds of 25000 rpm. End breakage rate in ring spinning is influenced by the quality of raw materials used, level of modernization and condition of machinery, type of opening and blending operations, regularity of draw frame sliver and roving, effective humidification control, use of optimum process parameters, efficient house-keeping and careful materials handling.

For a spinning mill, an increase in spindle speed leads to a reduction of overheads and wages costs per unit production. On the other hand increase in spindle speeds proportionately increases the load on drafting unit, Drafting speed will be increased with respect to spindle speed , drafting force gets increased in case of high draft ratio (in particular for processing long staple fibres).These factors directly or indirectly increase the mechanical load on cots & aprons. A spinning cot or an apron has to withstand these high speeds drafting with high draft ratio in order to deliver high quality yarns with better consistency.

Key words:

Draft, draft ratio, roller drafting, feed hank, delivery hank, apron surface speed, front cot surface speed, fibre pulling force, fibre gripping force , drafting force, resilience, abrasion resistance , wear and tear resistance.

Introduction:

Draft:

The amount of attenuation of textile material at different stages of spinning preparatory and spinning process, for example. 1 m of input material when delivered as 5 m is said to have undergone a draft of 5.In other words reducing the linear density of textile material with respect to time by passing the material through successive pair of rollers rotating at higher peripheral speeds.

Various formulas used in textile industry to calculate the draft as follows:

Drafting:

It is a process of reducing the bulk and weight per unit length of a semi processed textile material such as rove or sliver and simultaneously parallelizing its fibrous components, as it passes through the various machines used in making yarn