PROCESS PARAMETERS IN SIMPLEX

PROCESS PARAMETERS IN SIMPLLEX

           FOR ASSISTANCE CALL +91-98431-79009

PROCESS PARAMETERS IN SIMPLEX

IMPORTANT PARAMETERS

1.Feed hank

2.Delivery hank

3.Roving tension

4.Break draft

5.Type of drafting

6.Bottom roller setting

7.Top roller setting

8.Spacers

9.TM

10.End breakages rate

DRAFTING SYSTEM

                                                                                                     With 4 over 4 drafting system, the toal draft can be upto 13, whereas in the case of 3 over 3 drafting system , the draft can not be more than 11.

The Roving thickness and Roving hairiness(yarn hairiness) will be less with 4 over 4 drafting system compared to 3 over 3 drafting system.

In 4 over 4 drafting system, since the fully drafted material is just condensed in the front zone, if the stikiness in case of cotton or static in case of synthetic is high, then the lapping tendency will be very high on second top roller or second bottom roller. But in case of front roller, since the twist is penetrating upto the nip, lapping on the front bottom or top roller will be less.

As long as stickiness, honey dew in cotton and static in synthetic fibres is less, 4 over 4 drafting system with front zone as condensing zone, will give better results upto even 51 mm fibre.Of course the humidity conditions should be good

3 over 3 drafting system is good for fibres longer than 51 mm. 30 or 32 mm bottom roller diameters will be used with this system. Feed hank depends upon the total draft in speed frame. The drafts mentioned in the above table can be consdiered as a guide line. While processing 51 mm synthetic fibres, if the delivery hank is coarser,and the delivery speed is

verh high, the break draft and the back zone setting to be widened. Break draft and break draft setting does not depend only on T.M and fibre properties, it depends on the total production also. If the total production is very high, with low break draft and closer setting, roving breaks due to undrafted strand will increase.

Therefore, for very high production rate , higher break draft and wider break draft setting is required. This will result in very high "H" and "I" classimat faults(long thin faults). Therefore the breakage rate in

spinning will increase.

Break draft setting and break draft should be nominal. Abnormal break drafts and wider break draft settings indicate that there is a major problem in the process

KINKS IN DRAW FRAME SLIVER SLIVER

Some times draw frame coiling is a very big problem with synthetic fibres . If kinks are formed in the sliver, the kink has to be removed before entering the draft zone.

Kinks in the drawframe sliver depends upon

1.   drawframe delivery speed

2.   delivery can diameter

3.   coiler type

Higher the delivery speed, more the chances for kinks to be formed in the sliver. Lower the can diameter more the kinks. If a coiler which is meant for cotton is used, the kinks in the sliver will increase in case of synthetic fibres.

While processing synthetic fibres if kinks are more, it would be better if the creel is stopped. Sometimes it would be recommeded to use a rod between top arm and the first creel roll, so that the sliver takes a 90 degree bend before entering the top arm. This will help to remove the the kinks in the sliver. Otherwise, slubs in the roving will be more and the breakage rate in speed frame due to undrafted strand in the drafting zone will be more.

ROVING TENSION

The roving tension depends on the delivery rate and the difference between peripheral speeds of flyer and the bobbin. If the delivery length and the peripheral speed difference are same, then the tension is ideal.If

delivered length is more than the difference in peripheral speed , then the roving tension will be loose.

If the delivered length by the front bottom roller is less than the difference in pheripheral speeds of flyer and the bobbin, the roving tension will be tight.

Roving tension can be of three types

1.  Roving tension at the starting. It depends upon the Bare bobbin diamter and the Cone drum belt position

1. Roving tension during build-up. It depends upon the Ratchet wheel and lifter wheel. The difference between peripheral speeds of flyer and bobbin should be same and it should be slightly more than the length delivered by the front roller.

2.   Roving tension during up and down movement of the bobbin rail should be same. It depends upon the half tooth movement of the ratchet. If it is not exactly half tooth, then the tension will be different during up and down movement of the bobbin rail

3.   With modern machines, cone drum is removed. Bobbin speed, bobbin rail speed and flyer speed is determined by the computer depending upon the tension settings.In some machines, it can be programmed and the tension sensor helps to control a bit.In some makes, the tension setting totally depends upon the sensing by sensors.

The sensing accuracy depends upon the twist cap type, twist cape fixing, oil on top of twist cap etc. If only one roving tension is different due to various other reasons, then the entire machine tension will be altered. This is very dangerous. Enough care should be taken to avoid this problem.

4.   If lifter wheel is changed, then tension during build up will also change, the ratchet has to be selected accordingly. For a particular roving hank, ratchet wheel depends on Lifter wheel also.

5.   If the tension is low but unfiorm through out the bobbin, then the bobbin will be soft. Bobbin content will also be less. Chances of roving damages will be high.

6.   If the roving tension is more, then the stretch on the roving will be more, thin places will be more.

But it is better to increase the TPI little bit and increase the roving tension so that the bobbin content is more, roving damages are less, and creel stretch in the ring frame will also be less, because of higher TPI in the roving

OTHER FACTORS

It is better to adopt group creeling in speed frame. Because every piecing of sliver will result in a

thin and thick place. Therefore it is preferable to change 30 upto 60 cans together and remove the sliver piecing from the roving. Care should be taken so that no sliver piecing and roving piecing enters the ringframe and results in yarn.

This yarn always results in thin and thick places from .6 to 2 meters length. This will not be cut by the yarn clearers if the difference in size is less.

Roving Breaks in speed frame should not be more 1 to 2 per 100 spindle hours.If it is more than that, the reasons should be analysed and corrective action should be taken immediately.

Spacers should be as small as possible, to improve yarn quality. If slubs and roving breaks due to

undrafted is more, it would be better to use a bigger spacer(distance clip) instead of increasing the break draft and break draft zone setting to an abnormal level.

It is better to use good quality apron and rubber cots , since the quantity produced by one apron and

top roller is very high compared to ringframe. If the apron breaks and top roller damages are under control,

It is always better to use the best apron and rubber cots available in the market. One should not think about cost saving in this machine. Cost saving for apron and cots can be considered for ringframes.

Buffing should be done once in 3 months and the top roller shore hardness is around 80 to 85 degrees. After buffing, it is better to treat with acid or some special liquids which are being supplied to reduce lapping

Bottom and top clearers should rotate and should touch the top and bottom roller properly.

While processing cotton combed material, flyer speed is very critical. When the bobbin diamter is big, because of the centrifugal tension, surfact cuts will increase. i.e. roving breaks may occur at presser

or in strand that have just been wound on the top surface of the package. To avoid this problem, it is better to use inverter drive system, to reduce the flyer speed, when the bobbin diameter is big. Otherwise the overall speed should be less for the entire doff, this will reduce the production of speedframe. Sometimes, higher Twist will also reduce the surface cuts

PROCESS PARAMETERS IN DRAW FRAME

PROCESS PARAMETERS IN DRAWFRAME

    PROCESS PARAMETERS IN DRAW FRAME

FACTORS AFFECT YARN QUALITY ARE

1.Total draft

2.No of Draw frame passages

3.Break draft

4.No of doublings

5.Hank of sliver

6.Delivery speed

7.drafting type

8.Auto leveller & Auto leveller settings

SOME AIMPORTANT FACTORS

1.Wider back roll settings will result in lower yarn strength

2. Wider back roll settings will affect yarn eveness

3.Wider back roll setting will increase imperfections

4.Higher back top roll pressure will reduce strength

5.higher back top roll pressure will reduce end breaks

6.wider front roller settings will improve yarn strength

CAUSES OF DRAFTING WAVES

Drafting wave is caused primarily not by mechanical defects as such but by the uncontrolled fibre movement of a periodic type resulting from the defects. As the fibre-accelerating point moves towards the front rollers, the draft increases( and vice versa), so that a periodic variation in linear density inevitably results.

                                         

With variable fibre-length distribution(with more short fibre content), the drafting irregularity will be high.

More the number of doublings , lower the irregularity caused due to random variations. Doublings does not normally eliminate periodic faults.But it reduces the effects of random pulses. Doubling does not have any effect on Index of Irregularity also, since both the irregularities are reduced by square root of the number of doublings.

Fibre hooks influences the effective fibre length or fibre extent. This will affect the drafting performance. For carded material normally a draft 7.5 in both breaker and finisher drawframe is recommended. Seven of a draft can be tried in breaker, since it is a carded material.

For combed material, if single passage is used, it is better to employ draft of 7.5 to 8.

If combers with four doublings are used, it is better to use two drawframe passages after combing. This will reudce long thick places in the yarn.

In case of two drawframe passage, first drawframe passage will reduce the periodic variation due to piecing. Therefore the life of servomotor and servo amplifier will be more , if two drawframe passage is used. Quality of sliver will also be good, because of less and stable feed variation.

For synthetic fibres (44 mm to 51 mm), 8 of a total draft can be employed both in breaker and finisher passage.

The number of doublings depends upon the feeding hank and the total draft employed. Most of the modern drawframes are capable of drafting the material without any problem, even if the sliver fed is around 36 to 40 grams per meter.

         Especially for synthetic fibres with very high drafting resistance, it is better to feed less than 38 grams per meter to the drawframe.

Break draft setting for 3/3, or 4/3, drafting system is as follows

1.   For cotton, longest fibre +(8 to 12 mm)

2.   For synthetic fibre, fibre length + (20 to 30% of fibre length)

Break draft for cotton processing is normally 1.16 to 1.26. For synthetics it is around 1.42 to 1.6

To meet the present quality requirements , finisher drawframe should be an autoleveller drawframe.

Since the drawframe delivery speed is very high the top roller shore hardness should be around 80 degrees. It should not be less than that.

It is advisable to buff the rubber cots once in 30 days(minimum) to maintain consistent yarn quality.

Coiler size should be selected depending upon the material processed. For synthetic fibres, bigger coiler tubes are used. This will help to avoid coiler choking and kinks in the slivers due to coiling in the can.

Speed of the coiler will also affect the coiling. Speed of the coiler should be selected properly. In drawframes like RSB D-30(RIETER) , any coiler speed can be selected through the variator type pully. Since, the option is open, there is also more probability for making mistakes. One should take enough care to set the coiler speed properly.

Whenever coiler speed is adjusted, the diameter of the coil is also changed. Hence it is necessary to check the gap between the sliver and can. If it is more than 5 mm, then turn table position (can driving unit) should be altered so that the gap between coil outer and can inner is around 5 mm.

Pressure bar depth plays a major role in case of carded mixing and OE mixings. If it is open, U% will be affected very badly.It should always be combined with front roller setting. If the pressure bar depth is high,Creel height should be fixed as low as possible (esepcially for combed material).

Top roller condition should be checked properly. While processing 100% polyester fibres, fibre scum should be removed by a wet cloth from the top roller atleast once in a shift.

Sliver funnel size should be selected properly. Very wide funnel will affect the U%. But very small funnel will end up in more sliver breaks at the front.

If the department humidity variation is very big, then corresponding correction to be made for checking the wrapping of sliver ( sliver weight). Otherwise, there will be unwanted changes in the drawframe which will affect the count C.V.% of yarn.

Most of the Autoleveller drawframes are working on the principle of OPEN LOOP control system. Sliver monitor should be set properly. Whenever there is a problem in sliver weight, this will stop the machine. Sometimes sliver monitor may malfunction. If it is found

AUTOLEVELLING:

Most of the modern autolevllers are open loop autolevellers. This system is effective on short, medium and to some extent long tem variations.

Mechanical draft should be selected properly in autoleveller drawframes. To decide about the mechanical draft, drawframe should be run with autoleveller switched off.If the sliver weight is correct, then the mechanical draft selected is correct. Otherwise, the gears should be changed so that the sliver is weight is as per the requirement without autolevller.

Intensity of levelling and timing of correction are two important parameters in autolevellers.

Intensity of levelling indicates the amount of correction. i.e If 12% variation is fed to the drawframe the draft should vary 12% , so that the sliver weight is constant.

Timing of correction indicates that if a thick place is sensed at scanning roller, the correction should take place exactly when this thick place reaches the correction point(levelling point)

Higher the feed variation, higher the correction length. e.g. if feed variation is 1 %, and if the correction length is 8 mm, if feed variation is 5% the correction length will be between 10 to 40 mm depending upon the speed and type of the autoleveller.

Higher the speed, higher the correction length

Whenever the back roller setting, guide rails setting, delivery speed,break draft etc are changed, the timing of correction should also be changed.

U% of sliver will be high, if timing of correction is set wrongly

If intensity of levelling selected is wrong , then 1 meter C.V % of sliver will be high.

Most of the modern autolevellers can correct 25% feed variation. It is a general practice to feed 12% varition both in plus and minus side to check A%. This is called as Sliver test. The A% should not be more than 0.75%. A% is calculated as follows

If no of sliver fed to drawframe is N, Check the output sliver weight with "N", "N+1", "N-1" slivers. then

A% = ((gms/mt(N-1) - gms/mt(N))/ gms/mt(N) ) x 100

A% = ((gms/mt(N+1) - gms/mt(N))/ gms/mt(N)) x 100