Productivity Of A Spinning Mill
All spinners wish that the spinning productivity of
their mill (ring frame production in gms/spindle shift) has the optimum
level of efficiency. Though there are many aspects that limit the actual
production like ring diameter and its age, lift, age and make of the
ring frame, its maximum mechanical speed, type of spindle drive, lot
size, fluctuating production program, poor control on RH, lower HP of
main driving motor, greater percentage of untrained workers,
impoverished technical knowledge of subordinates etc.
Today, there is a pressure from the management to decrease the conversion cost to its lowest possible level because of cut throat competition in both the local and export markets. Ring spinning contributes approximately 70 per cent to the total conversion cost. Hence it is possible to speed up the ring frames to its maximum speed mechanically possible considering that spinning preparatory can feed ring frames at high speed. Also, neither the spinning performance nor the yarn quality is adversely affected by such speeding up of the ring frames.
Currently many spinning mills in India are capable of managing their ring frames at actual great speeds quite successfully counts 30s-40s at 20/21/22,000 rpm and finer counts - 60s-76s at up to 24,500 rpm and yet maintaining identical breakage rate of 2-3 breaks/l00 spindle hrs that they were earlier performing at 15/16,000 rpm. Also, the yarn quality has not been affected.
Factors that affect spinning productivity
Many factors that affect spinning productivity/end breakages/ yarn properties/ yarn complaints are mentioned here. Increasing productivity is not just gearing up the ring frames but making many efforts such as arranging proper fibres bales to blowroom in a particular direction, maintaining product quality at spg preparatory machines, care of cots and aprons, QC checks, etc., to make sure that spinning breakages, winding breaks, vital yarn properties and quality of yarn at the looms should not deteriorate at all.
Polyester staple fibre associated factors
Change the fibre denier, if possible, to the next stage i.e. if a mill is using 1.4 Den fibre, they can use 1.2 Den. Several advantages here are 20-25 per cent higher number of fibres in the cross section giving to superior yarn strength, improvement in uster value, lesser imperfections and reduced hairiness - which in turn improves weaving performance up to 4-6 per cent with Sulzer weaving machines.
The 'compromise' cut length is 44 mm, though it is believed that in the next 5 years or so, mills will change to 38 mm as is the practice world wide.
Many fibre manufacturers give actual values of important fibre properties with each dispatch. How much the mill technicians consider these values provided by the fibre manufacturers is a debatable issue. It has been seen that most of the mill technicians do not have the proper knowledge to evaluate these values of fibre properties. Of course, it is a good idea if the fibre manufacturers provide the information.
In fact the actual values of the following fibre properties should be given with every dispatch:
. Actual denier
. CV% of denier
. Actual tenacity gms/denier
. Actual per cent elongation at break
. T10gms/denier
. Crimps / 25 mm
. Crimp stability
. Crimp take-up
. Actual oil pick-up and its variation. Actual Dry Heat Shrinkage (@ 180°C for 30 minutes)
. Fused fibres (in mg/10 kg of raw fibre)
. Over lengths/multi lengths - Number per 10 gms
. Actual b colour
Polyester fibre bales to blowroom
Most fibre manufacturers should make sure that dispatch of bales is done in serial order. The reason is that the bales are placed in the warehouse in that order. Today's fibre plants are highly productive. Limits sets in which it make about 120 tons/day, are common. Hence a truck load of bales get made in just 2 hrs or so.
The fibre properties do not vary within 2 hrs, but if it takes more days or say a week, many fibre properties do change some times even outside the set limits. So it helps day' variations are taken care of very well. This ensures smoother running of fibres and no problems of rings under UV and dye variation in the final fabric
It is noted that holding a stock of more than 4 or 6 trucks constantly involves blocking of capital, but
. Ensured no complain of dye variation - streaks warp way and bars weft way
. Ensured no problem of rings under UV lamps.
Hence the benefit received outweighs the extra financial burden. Many mills that have been pursuing this and have gained fully the 3 plus points privilege of above. In Indonesia, many mills utilize Blendomats where 36 bales are placed at one time, hence blending of fibres made on different days.
Performance at spinning preparatory machines
Check that all mechanical data total/break drafts, roller settings, TM (Twist Multiplier) etc, even trumpet diameter is completely matching on each and every machine working on one mixing. Changes in C.P (Change Pinion for change in draft) to be done on 'group' basis according to the material being used so as to have minimum machine variations.
Though blending for bales produced is important, it is likewise important to:
1. Number the card cans
2. Check that all cards working on a mixing are represented in the creel of the breaker draw frame
3. Use cans of two different colours at the two deliveries of breaker draw frame
4. Place 4 cans of each colour in the creel of the Finisher Draw frame.
In this way one will have intimate fibre to fibre blending.
Verify all stop motions at both breaker and finisher draw frame and check whether these are functioning well. Also check that the auto leveler is functioning properly.
Check winding tension on the roving remains identical throughout the build of the roving bobbin. Check this by getting 4 full roving bobbins - 2 from front row and 2 from back row; get at least 5 wrappings and work out the average. Place empty roving bobbins on the same 4 spindles and operate the machine until approximately 200 metres is wound up; then detach bobbins and verify wrappings. The variation between the average of wrappings of 'full' and 'empty' bobbins should be less than 2 percent.
Check that no roving bobbin with Uster U percent of greater than 3.5 is sent to ring frames. In order to verify this, check Uster U percent of each and every roving bobbin from a frame once every month. Spot out if there are any arms that are producing off spec bobbins. Get the top arms attended to and recheck the Uster U percent.
Check that the drafting device at the fly frame is only adding 'allowable' unevenness. By having Uster U per cent of finisher sliver, apply the following formula to envisage roving U per cent (U per cent of roving x 1.25)2 = (U per cent of Finisher drawing x 1.25)2 + K, K may be considered as 10.
If the actual roving U per cent is considerably greater than the expected U per cent value, then go for the drafting system, checking conditions of rollers, cots, aprons, roller pressure, setting, draft distribution etc. One feasible cause could also be that the total draft is too high. Also check by inspecting Spectrograms of rovings with greater U per cent that there is no interrupted work.
It is important to verify the condition of each and every cot and apron in the mill very frequently, which is practiced daily in Indonesia and once a week by a senior person in India; and any faulty cot/apron is right away put back.
It is noted that if the finisher drawing sliver's U per cent is 1.6; CV per cent of wrapping is 0.22 and the spectrogram proves no interrupted irregularity, then this sliver will function at fly frame with practically zero break; and this roving will function on ring frames with 2/3 breaks/100 spindle hrs at ring frame working at real high speed considering ring spinning is well managed but in real life - mainly in textile industry sometimes something else will happen and mill could end up with 10 breaks/100 spindle hrs at high speed.
Ring Frame control
Considering that a spinning mill has accepted all the steps mentioned above, even then the following points need to be focused upon:
Make sure that mechanical data is matching on all ring frames working on one mixing, changes in change pinion be done on 'group' basis. If the actual roving U per cent is considerably greater higher, then, go for the drafting system, conditions of rollers, cots, aprons, roller pressure, setting, draft distribution etc.
Cots and aprons should be tested daily - or at least once in 2/3 days. Also ring travellers should be altered on schedule.
To get a pulse on the functioning at ring frames, best is for the spinning manager himself to carry out snap round compromising all ring frames for number of spindles per frame not making yarn at various intervals of the day. This snap round does not bear much time. A worksheet to be maintained in the department with the following data:
. Date
. Time at start of Round
. Time at end of Round
. Dry Bulb degree Celsius
. Wet Bulb degree Celsius
. RH per cent
. Idle spindle report due to the below mentioned reasons:
1. Spindle break
2. Lapping: top roller, bottom roller
3. Roving: break
exhausted
4. Mechanical
5. Other
It is noted that taking snap rounds is up to 2 spindles not making yarn per frame is pragmatic in good Indian mills and as low as less than 1 spindle not making yarn per frame in good Indonesian mills. In general, if a mill has 2 spindle or less not making yarn/frame (irrespective of the no. of spindles/ frame) then the mill is performing well.
At last consider control on Relative Humidity. A lot of spinning mills still apply wet and dry bulb thermometers. (Many a times water is not placed in wet bulb). The perfection here is exclusively dependent on the perfect judgment of the person who notes down the temperatures. However meters with digital display of both temp and RH are offered, it is recommended putting thermo hygrographs note down temperature and RH continuously for say 24 hrs. Every morning the spinning personnel should check the shape of the trace mainly of RH and in this regards they have to maintain some kind of standardized RH in the department.
There was doubt that with high speed spinning, traveller temperature will increase to blend polyester fibres in the yarn. Luckily nothing like this has happened and blend spinners can carefully run their ring frames even at 25,000 rpm.
Conclusion
It is observed that if a spinning mill follows the steps recommend as above, they can function their ring frames at speeds up to 25,000 rpm without either rising the breakage rate weakening yarn quality. The recommendation provided here is based on experts' experience of functioning with many spinning mills in India and Indonesia increases spinning productivity.
Today, there is a pressure from the management to decrease the conversion cost to its lowest possible level because of cut throat competition in both the local and export markets. Ring spinning contributes approximately 70 per cent to the total conversion cost. Hence it is possible to speed up the ring frames to its maximum speed mechanically possible considering that spinning preparatory can feed ring frames at high speed. Also, neither the spinning performance nor the yarn quality is adversely affected by such speeding up of the ring frames.
Currently many spinning mills in India are capable of managing their ring frames at actual great speeds quite successfully counts 30s-40s at 20/21/22,000 rpm and finer counts - 60s-76s at up to 24,500 rpm and yet maintaining identical breakage rate of 2-3 breaks/l00 spindle hrs that they were earlier performing at 15/16,000 rpm. Also, the yarn quality has not been affected.
Factors that affect spinning productivity
Many factors that affect spinning productivity/end breakages/ yarn properties/ yarn complaints are mentioned here. Increasing productivity is not just gearing up the ring frames but making many efforts such as arranging proper fibres bales to blowroom in a particular direction, maintaining product quality at spg preparatory machines, care of cots and aprons, QC checks, etc., to make sure that spinning breakages, winding breaks, vital yarn properties and quality of yarn at the looms should not deteriorate at all.
Polyester staple fibre associated factors
Change the fibre denier, if possible, to the next stage i.e. if a mill is using 1.4 Den fibre, they can use 1.2 Den. Several advantages here are 20-25 per cent higher number of fibres in the cross section giving to superior yarn strength, improvement in uster value, lesser imperfections and reduced hairiness - which in turn improves weaving performance up to 4-6 per cent with Sulzer weaving machines.
The 'compromise' cut length is 44 mm, though it is believed that in the next 5 years or so, mills will change to 38 mm as is the practice world wide.
Many fibre manufacturers give actual values of important fibre properties with each dispatch. How much the mill technicians consider these values provided by the fibre manufacturers is a debatable issue. It has been seen that most of the mill technicians do not have the proper knowledge to evaluate these values of fibre properties. Of course, it is a good idea if the fibre manufacturers provide the information.
In fact the actual values of the following fibre properties should be given with every dispatch:
. Actual denier
. CV% of denier
. Actual tenacity gms/denier
. Actual per cent elongation at break
. T10gms/denier
. Crimps / 25 mm
. Crimp stability
. Crimp take-up
. Actual oil pick-up and its variation. Actual Dry Heat Shrinkage (@ 180°C for 30 minutes)
. Fused fibres (in mg/10 kg of raw fibre)
. Over lengths/multi lengths - Number per 10 gms
. Actual b colour
Polyester fibre bales to blowroom
Most fibre manufacturers should make sure that dispatch of bales is done in serial order. The reason is that the bales are placed in the warehouse in that order. Today's fibre plants are highly productive. Limits sets in which it make about 120 tons/day, are common. Hence a truck load of bales get made in just 2 hrs or so.
The fibre properties do not vary within 2 hrs, but if it takes more days or say a week, many fibre properties do change some times even outside the set limits. So it helps day' variations are taken care of very well. This ensures smoother running of fibres and no problems of rings under UV and dye variation in the final fabric
It is noted that holding a stock of more than 4 or 6 trucks constantly involves blocking of capital, but
. Ensured no complain of dye variation - streaks warp way and bars weft way
. Ensured no problem of rings under UV lamps.
Hence the benefit received outweighs the extra financial burden. Many mills that have been pursuing this and have gained fully the 3 plus points privilege of above. In Indonesia, many mills utilize Blendomats where 36 bales are placed at one time, hence blending of fibres made on different days.
Performance at spinning preparatory machines
Check that all mechanical data total/break drafts, roller settings, TM (Twist Multiplier) etc, even trumpet diameter is completely matching on each and every machine working on one mixing. Changes in C.P (Change Pinion for change in draft) to be done on 'group' basis according to the material being used so as to have minimum machine variations.
Though blending for bales produced is important, it is likewise important to:
1. Number the card cans
2. Check that all cards working on a mixing are represented in the creel of the breaker draw frame
3. Use cans of two different colours at the two deliveries of breaker draw frame
4. Place 4 cans of each colour in the creel of the Finisher Draw frame.
In this way one will have intimate fibre to fibre blending.
Verify all stop motions at both breaker and finisher draw frame and check whether these are functioning well. Also check that the auto leveler is functioning properly.
Check winding tension on the roving remains identical throughout the build of the roving bobbin. Check this by getting 4 full roving bobbins - 2 from front row and 2 from back row; get at least 5 wrappings and work out the average. Place empty roving bobbins on the same 4 spindles and operate the machine until approximately 200 metres is wound up; then detach bobbins and verify wrappings. The variation between the average of wrappings of 'full' and 'empty' bobbins should be less than 2 percent.
Check that no roving bobbin with Uster U percent of greater than 3.5 is sent to ring frames. In order to verify this, check Uster U percent of each and every roving bobbin from a frame once every month. Spot out if there are any arms that are producing off spec bobbins. Get the top arms attended to and recheck the Uster U percent.
Check that the drafting device at the fly frame is only adding 'allowable' unevenness. By having Uster U per cent of finisher sliver, apply the following formula to envisage roving U per cent (U per cent of roving x 1.25)2 = (U per cent of Finisher drawing x 1.25)2 + K, K may be considered as 10.
If the actual roving U per cent is considerably greater than the expected U per cent value, then go for the drafting system, checking conditions of rollers, cots, aprons, roller pressure, setting, draft distribution etc. One feasible cause could also be that the total draft is too high. Also check by inspecting Spectrograms of rovings with greater U per cent that there is no interrupted work.
It is important to verify the condition of each and every cot and apron in the mill very frequently, which is practiced daily in Indonesia and once a week by a senior person in India; and any faulty cot/apron is right away put back.
It is noted that if the finisher drawing sliver's U per cent is 1.6; CV per cent of wrapping is 0.22 and the spectrogram proves no interrupted irregularity, then this sliver will function at fly frame with practically zero break; and this roving will function on ring frames with 2/3 breaks/100 spindle hrs at ring frame working at real high speed considering ring spinning is well managed but in real life - mainly in textile industry sometimes something else will happen and mill could end up with 10 breaks/100 spindle hrs at high speed.
Ring Frame control
Considering that a spinning mill has accepted all the steps mentioned above, even then the following points need to be focused upon:
Make sure that mechanical data is matching on all ring frames working on one mixing, changes in change pinion be done on 'group' basis. If the actual roving U per cent is considerably greater higher, then, go for the drafting system, conditions of rollers, cots, aprons, roller pressure, setting, draft distribution etc.
Cots and aprons should be tested daily - or at least once in 2/3 days. Also ring travellers should be altered on schedule.
To get a pulse on the functioning at ring frames, best is for the spinning manager himself to carry out snap round compromising all ring frames for number of spindles per frame not making yarn at various intervals of the day. This snap round does not bear much time. A worksheet to be maintained in the department with the following data:
. Date
. Time at start of Round
. Time at end of Round
. Dry Bulb degree Celsius
. Wet Bulb degree Celsius
. RH per cent
. Idle spindle report due to the below mentioned reasons:
1. Spindle break
2. Lapping: top roller, bottom roller
3. Roving: break
exhausted
4. Mechanical
5. Other
It is noted that taking snap rounds is up to 2 spindles not making yarn per frame is pragmatic in good Indian mills and as low as less than 1 spindle not making yarn per frame in good Indonesian mills. In general, if a mill has 2 spindle or less not making yarn/frame (irrespective of the no. of spindles/ frame) then the mill is performing well.
At last consider control on Relative Humidity. A lot of spinning mills still apply wet and dry bulb thermometers. (Many a times water is not placed in wet bulb). The perfection here is exclusively dependent on the perfect judgment of the person who notes down the temperatures. However meters with digital display of both temp and RH are offered, it is recommended putting thermo hygrographs note down temperature and RH continuously for say 24 hrs. Every morning the spinning personnel should check the shape of the trace mainly of RH and in this regards they have to maintain some kind of standardized RH in the department.
There was doubt that with high speed spinning, traveller temperature will increase to blend polyester fibres in the yarn. Luckily nothing like this has happened and blend spinners can carefully run their ring frames even at 25,000 rpm.
Conclusion
It is observed that if a spinning mill follows the steps recommend as above, they can function their ring frames at speeds up to 25,000 rpm without either rising the breakage rate weakening yarn quality. The recommendation provided here is based on experts' experience of functioning with many spinning mills in India and Indonesia increases spinning productivity.
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