Tuesday, 30 September 2008

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.

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