Cost of Warping

Warping process is required exclusively for preparing warp yarn for weaving. Hence warping cost should be calculated for warp yarn.

Unit costs in this section can be developed on weight basis or on length basis.

Weight Basis

Warping cost per piece length of fabric= weight of warp yarn per length x cost per unit weight.

If unit costs are developed on length basis, they are expressed with reference to specific number of ends (generally 400-500 ends). It follows , therefore, that about four to eight beams ( some time even more) would be required to made one beam for weaving.

In other words, unit cost in terms of length will have to be multiplied by the number of warp beams required per weaving beam. Then warping cost per piece length of a fabric can be calculated as shown:

warping cost per piece length of fabric = cost per meter x tape length x no of warp beams per weaving beam.

If the warp beam is partly colored and partly greige, warping cost should be calculated for greige warp yarn and coloured warp yarn. Generally coloured yarn is processed on slow speed warping frame. Hence cost of color warping usually works out higher as compared to the cost of greige warping.

control of end breaks in warping

Minimising end breaks in warping involves four steps namely:

1. Control of tension in the yarn
2. Satisfactory maintenance of those machines
3. Minimising the defects on packages produced at winding
4. A regular check on the end breakage rate for comparison with the norm.

1. conrol of tension in the yarn

On the warping machine, there are two types of variation in yarn tension
1. Between different stages of unwinding of a package. This can be detected after the first thread guide.
2. Between ends. It can be detected at the head stock.

The tension variation that occurs during the unwinding of a package can be minimised if you design the creel such that the distance between the package and the first thread guide is shortest, it will avoid the yarn balloon rubbing the nose of the package.

The tension variation between the ends at the headstock is minimised if the groups of neighbouring ends on the beam are taken from the same column of packages in the creel.

2. Condition of Machine

a. Alignment of the package at the creel

Non alignment of the creel package with respect to the first guide is often seen to be a cause of high end breakage rate at warping. This alignment is done with the help of a gauge.

b. Eccentric Guide rollers

On machines with mechanical stop motions, there are several guide rollers at the headstock which are positioned very near to one another. Eccentricity in those rollers can introduce short term tension variations of high amplitude.

c. Thread Guides

Deep cuts in thread guides can significantly increase yarn tension and hence deteriorate warping performance. If found dirty, the thread guides should be cleaned with CCl4.

d. Relative humidity and temperature

For satisfactory working at warping, about 60% RH should be maintained. The dry bulb temperature should be kept at about 29 o C (84 o F). Lower humidity may increase yarn hairiness, end breaks and liberation of fluff. The fluff ultimately passes to the beam and given difficulty during sizing. Higher humidity is unnecessary; in fact relative humidity higher than 70% may increase end breakage rate.

Process Control in Warping-3

Process Control in Warping-3

Maintenance Check points at Warping

Machine

1. Clean with compressed air at every creel change-per shift
2. Clean with compressed air and cleaning waste- weekly

Package Alignment at the Creel

1. Look for incorrectly aligned packages, correct if the non-alignment is too severe- regularly
2. completely guage the creel with the help of a gauge- half yearly

Tension Weights

In case of high speed warping machine, check tension weights at every count change- regularly

Tension Level

Check the tension levels with tension meter- Monthly

Stop Motion and Brake

1. Ensure that the machine stops within 1 1/2 revolutions fo the drum in case of high speed warping- regularly
2. Check with condition of drop pins and replace those with cut marks- regularly.

Guide rollers

1. Check for concentricity- half yearly

Beams
1. Check for the conditions of flanges and beam shafts, repair damaged beams- regularly

Creel Fans
1. Check that creel fans oscillate properly and are not chocked with fluff- regularly.

Parts in yarn path

1. Check for cuts in parts of machine in yarns parts regularly.
2. repair/replace the parts with cut marks- weekly

Process control in warping-2

Efficiency of Warping Department

The following will calculate the efficiency of a warping machine:

Let Speed in m/min= 300
Set length (m) = 18000
Yarn length on cone/cheese (m)= 54000
Number of Ends/beam= 500
end breaks/400 ends/ 1000 m = 3
Time to mend a warp break (seconds) = 35
Time to change a beam (seconds) = 500
Time to change a creel (seconds) = 3000
Time loss due to miscellaneous causes/1000 m (seconds)= 25

Calculation

Running time R (s) = 1000x60/300 = 200
R is the uninterrupted running time in meters
Breaks/running ends in beam/1000 m = 3x500/400 = 3.75
Stoppage time /1000 m
(a) to mend breaks (s)= 3.75x35 =131 s
(b) to change a beam (seconds) = 500x1000/18000 = 28 s
(c) to change a creel = 3000x1000/54000 = 56 sec
(d) Miscellaneous time = 25 seconds

Therefore, S, the total stoppage time per 1000 meters (s)= 131+28+56+25 = 240 s

Therefore total efficiency = Rx100/(R+S)= 200x100(200+240) = 45.5 %

Expected Production per shift of 8 hours (m) = (300x60x8x45.5)/100 = 65,500 m

Causes of Low efficiency or Low productivity

1. Increase in End breakage rate

The machine efficiency at warping is highly sensitive to the end breakage rate

2. Improper utilisation of magazine creel

If the creel boy does not keep the magazine creel ready to be used by the time the package in the running creel are over, the efficiency will fall.

3. Reduction in Average Set-length

Lower set lengths reduce the machine efficeincy at warping

4. Number of Tenters per Machine

The number of tenters per machine determine the time to mend an end break. This is because by the time the warper finds a broken end on the beam, the creel boy brings the other end of the broken yarn from the creel

5. Stops due to Machine Breakdown, shortage of cones etc.

If the stops due to machine breakdown, shortage of empty beams or cones/cheeses etc. are high, the actual efficiency of the machine will be lower than calculated.