S. Sudarshan

ITEMA, Service engineering, Coimbatore

sudhhan@gmail.com

P. Ganesan & S. Hariharan

Department of Textile Technology,

PSG College of Technology

ganeshg007@rediffmail.com & shariharan108@gmail.com

Abstract

Unlike in winding, warping and sizing where the emphasis is on the quality of preparation, in the loomshed, control of fabric quality as well as of productivity assume significant importance. The weaving operation contributes by far the largest proportion to the cost of conversion of yarn into fabric. Surveys shown that the cost of actual weaving operation in mills with modern preparatory machines and automatic looms about 65% of the total cost for conversion of yarn into fabric.

This means that a small increase in loomshed efficiency via productivity will result in considerable reduction of manufacturing cost. More importantly an increase in efficiency will bring in additional realization on the extra fabric available. For a medium size average mill, an increase of 2% in loomshed productivity can increase the annual cash flow by about Rs. Six lakhs. Consequently, in evolving a satisfactory process control programme for the loomshed, considerable weightage should be given to efficiency.

Key words: Projectile loom, Weaving, productivity, efficiency losses.

1. Introduction

Generally, loomshed efficiency is calculated for each shift on the basis of production. In loomshed, the production is measured in terms of either pieces booked, metres woven or picks inserted. This method of calculation only gives an idea of the efficiency achieved. It does not indicate the performance index of a mill in relation to an expected optimum. In order to know exactly what a mill can achieve, it is necessary to have standards for efficiency losses due to various causes and a method of estimating the expected efficiency under a given set of circumstances.

The causes for efficiency losses in looms can be divided into two broad categories as frequency dependent and miscellaneous. Warp and weft breaks, beam gaiting belongs to first category, where as healds broken, doffing, loom repairs, weave away, etc. are termed as miscellaneous causes. Interference is, yet, another cause of stoppage. Its extent depends upon the number of looms assigned to a weaver and frequency of warp and weft breaks. Miscellaneous causes are those occurring at random. Further, such causes cannot be ascribed any definite frequency. Whenever an operator is in charge of more than one machine, there is loss due to interference. On looms, this loss is observed to be essentially a function of such stoppages as warp breaks, weft breaks and hence for all practical purposes, it may be expressed as a percentage of the total loss on account of these causes.

The efficiency losses arising from loom stoppages in looms are generally of two types such as those requiring the weavers attention and those not requiring weavers attention. The former category includes causes like warp breaks, weft breaks and interference. Losses due to warp and weft breaks are in proportion to the frequencies. The interference loss is depend upon the loom assignment to weavers, frequency of warp and weft breaks, average distance required to be walked per stoppage and other miscellaneous jobs performed by a weaver. Losses due to stoppages not requiring weavers attention arise from loom repairs, cleaning and oiling, beam gaiting and others. Efficiency loss on account of beam change varies according to its frequency, while other losses depend upon the organizational setup, frequency of breakdowns, types of looms, sorts woven and level of maintenance.

As stated earlier, efficiency losses due to warp and weft breaks and beam gaiting of frequency dependent and hence they vary from mill to mill and also sort to sort within the same mill. On the other hand, efficiency losses, ascribable to loom repairs, cleaning and oiling, doffing and other stoppages are observed to be of more or less the same order between mills. For all practical purposes, it would be quite in order to provide an overall allowance for the losses arising from these causes.