Wednesday, November 5, 2014
Maximum traveller speed – It is limited by the types of ring flange, style of traveller, wt. of traveller and rate of traveller run.
Maximum roller delivery speed – The limiting factors beings the ability of the operative to piece-up the broken ends and the limitation of the drafting system to control fibres.
Yarn tension in the balloon – The limiting factors being sufficient strength in the processed yarn to withstand the tension imposed by the traveller and balloon. The amount of twist can alter the yarn strength irrespective of type and staple of fibres.
Balloon collapse – It is caused by operating with high spindle speed and low traveller weight. Yarn strength being enabled to support a heavy traveller.
Limitation of drafting system
Final requirements of spun yarn
What are the important setting points in ring-frame?
The important setting points are –
1. Roller setting.
2. Lappet rail setting.
3. Lappet snarls setting.
4. Spindle rail setting.
5. Spindle setting.
6. Ring rail setting.
7. Setting of the building mechanism.
8. Setting of the fulcrum for different tapper shapes.
9. Setting of the roving guide traverse motion.
10. Setting of the top roller angle with the bottom roller.
11. Adjusting top roller pressure on the bottom rollers.
The functions of ring are –
The functions of ring are –
a. The ring guides the circular run of the traveller.
b. The ring act as a high speed bearing surface for the travellers.
c. One may also conceive the behavior of the ring as a track for the traveller.
It performs the following functions –
a. Twisting of the drafted strand of fibres as they are delivered by the front roller to produce a yarn.
b. Winding of yarn onto the bobbin.
c. Maintain winding tension of the yarn by the frictional resistance between the ring and traveller.
d. It acts as a second guide for the yarn on the way to be wound on the bobbin.
e. It performs the function of building motion to wind the constant length of yarn delivered by the front roller. In speed frame bobbin r.p.m changes with the increase of bobbin diameter but in ring frame the bobbin r.p.m remains constant and the traveller r.p.m increases with the increase of bobbin diameter.
It also performs many other functions involving highly complicated problems of higher physics.
The function of the creel is to hold the roving bobbin over a roller beam within a convenient height to easily handle the roving. The creel must permit free running of the roving bobbins with slight tension on it.
a. The spindle holds the bobbin somewhat loosely but tight enough to prevent any slippage, so that the bobbin can be lifted out of the spindle with little exertion.
b. With the help of the ring and traveller the spindle inserts twist in the yarn being delivered by the front roller.
c. It also carries out another important function of winding the twisted thread on the bobbin with the help of ring and traveller.
Roving guide –
The guides are mounted at the right angle to the flat bar called traverse bar. The object of the guide is to feed the roving correctly at the bite of the back roller and the traverse motion moves the strand almost over the entire length of the bite and this prevents the drafting rolls from being grooved at a particular place.
Lappet motion or thread board traverse –
The main function of the thread board traverse is to maintain the balloon size within the controlling range. To keep the balloon length within the controlling limit, the thread board is necessarily be made to traverse relative to the ring rail. For 8” lift bobbin the traverse of the ring rail is more or less confined within the range from 1” – 1.5” and higher traverse for higher lift of the machine.
The slow traverse of lappet-rail also facilitates the easy passage of the yarn from the front roller to the bobbin.
Classify the drafting systems used at the ring frame with example and explain a modern system
Drafting system can be broadly classified under two heads namely –
1. Regular drafting system without apron. And
2. Drafting system with apron.
The system with apron can again be classified into three groups –
1. Single apron system.
2. Double apron system. and
3. Multiple apron system.
Example of regular drafting system without apron –
a. Conventional three roller system.
b. Improved system.
c. H and B four rollers long draft system.
d. 5 over 4 roller systems.
Example of single apron drafting system –
a. Saco – Lowell. Both systems.
b. Saco – Lowell. Shaw system.
c. Saco – Lowell. Z system.
d. Toenniessen system. and
e. Versatex LS system.
Example of double apron drafting system –
a. Casablancas double apron system.
b. Casablancas “L” system with flexible bar.
c. Saco – Lowell thread rollers duo-Roth system.
d. SKF pendulum top arm weighting system. And
e. Saco – Lowell 4 – roller Duo – Roth system.
Example of multiple Apron drafting system –
a. Casablancas “N” system.
b. Nittoh’s Semi-super high draft system.
c. OM – S super high draft system.
OM – Super high draft system –
This system is specially designed to spin direct from drawing sliver using special size small sliver cans in place of usual roving bobbin in the creels as shown in the figure below fig. –
The back draft zone is in vertical position and the front zone is inclined position to 500. The rollers are spring weighted. In this system the back draft zone is equivalent to the draft of a sliver and the drafting arrangement resembles to that of the long draft sliver (Back, 4th and 3rd rollers). The front zone (3rd, 2nd, and front roller) resembles the ordinary Casablancas system.
It is claimed that, draft from 300 – 400 for count of 60s – 80s and 150 – 250 for count 20s – 40s can be obtained.
Monday, November 3, 2014
The faults found in ring frame yarn and their causes are given below –Soft yarn – Generally caused by slack spindle bundles, twist change wheel too large, empty bobbins not properly pushed down during doffing.
Uneven yarn – Either travellers are too heavy or for spinning fine counts from inferior cotton.
Fuzzy yarn – Rings too large, by ballooning or bad lubrication of ring frame rollers.
Twisty and brittle yarn – Worn rings and travellers are too heavy or lack of humidity in spinning room.
Rough yarn – Traveller too light, too much twist, and spindle speed too low, bobbins that are rough at the top.
Badly wound yarn – Caused by the defective traveller motion and also by bobbin being loose on the spindle.
Tender yarns – Imperfect traveller, waste on travellers, adjustment of ring rail not correct, thread guide not in the right position.
Hard and inelastic yarn – Too much twisting and drafting in the draw frame and also for insufficient doubling later.
Slub – This occur when the twist in the yarn is not uniform. It appears as thick place, which has received insufficient twist. This is caused by what is called thick roving. Two rovings over lapping each other, which thus passing through the rollers without receiving the amount of twist required.
Nepped yarns – So called because it contains small piece of hard cotton called neps. These are two kinds: Commonly distinguish as natural neps and will neps. The former consists of short and undeveloped fibres that have become embedded in the yarn. The latter are impurities and also short fibres usually found adhering to the surface of the threads.
Sunday, November 2, 2014
The causes of end down in ring frame are as follows –
Skewer – Bad skewer ends or tips or any other fault which prevent the free rotation of the roving bobbin.
Traverse guide on roving guider –
a. Traverse guide when collecting fly blocks the regular passage of the roving.
b. No middle traverse guide when using double roving.
a. Bad piecing in the roving.
b. Stretched roving.
c. Irregular roving.
d. More twist applied in the roving leading to “shedding through” at the ring.
e. Single roving when using double.
f. Neps or slubs in the roving.
g. More waste in the roving.
Drafting zones –
a. Incorrect break draft.
b. Roller lapping.
c. Worn or grooved roller.
d. Rust on the bobbin drafting.
e. Worn aprons.
f. Pneumatic system does not work properly so that the drafted strand of fibres fly entangles with the side end and cause breakage.
g. Irregular distribution of draft in the drafting zones.
h. Incorrect weight distribution on the top roller.
i. Improper weighting of the top roller.
j. Incorrect setting of the drafting rollers in relation to the average staple length of fibres under processing.
Lappet rail –
a. Incorrect setting of the lappet is not at the straight line with the top of the spindle.
b. Dwell at each end of the traverse of the lappet rail.
c. Starting up of the m/c when the lappet rail is at the top position.
a. Worn ring.
b. Grease or gum on and under side of the ring flange.
a. Heavy or lighter traveller than that required for the count.
b. Worn traveller.
c. Traveller flying off.
d. No traveller clear creating tufts of fibre on the traveller.
a. Lack of lubrication in the bolster cage or insert.
b. Bent spindle is out of centre of the spindle.
c. Excessive spindle speed than that requires for the count.
d. Obstructed spindle speed by accumulation of fibres beneath the spindle.
a. Too larger or smaller diameter of bobbin than that suitable for the count.
b. Jumbling bobbin.
c. Vibrating bobbin.
d. Badly worn bobbin in which yarn tends to catch at the starting up.
e. Excessive full bobbin which rub against the ring.
a. Bad joining of tapes causing spindle vibration.
b. Tap ends flying off due to badly sewing.
c. Slipping tapes.
a. Use of higher or lower twist multipliers than that requires for the count.
Other causes –
b. Flying fibres.
c. Incorrect relative humidities.
d. Wind in the spinning section.
e. Bad piecing up of the yarns.
f. Shorter staple when used for higher count.
g. Immature short or broken fibres in the sliver.
h. Weaker fibres.
i. Improper lubrication of the m/c.
j. Lack of proper cleaning of the m/c floor.
k. Irregular maintenance and over haul.
Friday, October 31, 2014
What is ballooning effect? What are the factors, which effect the degree of ballooning and how can be controlled?
During spinning operation the drafted strand of fibre being delivered and held at one end by the front rollers, the other end rotates round the bobbin with the traveller on the ring. It is observed that the thread between the thread guide and the traveller, is bulged out which is called the ballooning effect if the thread; and the balloon runs around the bobbin at a high speed equal to the speed of the traveller.
The following factors effect the degree of ballooning –
The weight of the balloon length – The length of the yarn which shows the ballooning effect is called the balloon length. The degree of ballooning varies inversely as the wt. of the balloon length i.e. higher the balloon length-weight, smaller the balloon size.
Yarn count – The degree of ballooning varies directly with the yarn count i.e. higher the yarn count, lighter the yarn and higher the balloon size.
Speed of the traveller – Higher the speed of the traveller, larger the balloon size.
Weight of the traveller – Lighter the traveller, larger the balloon.
Atmospheric resistance surrounding it – Higher the resistance, smaller the balloon.
Frictional resistance at the thread guide and at the traveller against the passage of the thread – Higher this resistance, smaller the balloon size.
The effect of item no. 5 and 6 is little on ballooning. The following measures may be taken to control the ballooning –
- The use of correct traveller size.
- The use of correct traveller speed.
- The use of separator or balloon guards between the two rings.
- By lowering the thread-guide rail to the correct position.
Thursday, October 30, 2014
The chief characteristics of the spindle for good running conditions –
The following important characteristics of the spindle should always be kept for good running condition –
a. It should run with its vertical axis strictly perpendicular to the rail-base on which the ring is mounted; both the spindle and the ring should be concentric to one another.
b. The spindle blade should never be allowed to run with defective insert.
c. It should run well balanced.
d. It should run with minimum friction and should have precise construction with minimum tolerance to ensure smooth and vibration free running even with variable loads on the bobbin as the yarn is wound on it under tension.
The plumbing and setting of the spindle –
Correct plumbing of the spindle is very important art and requires a skilled hand. This correct operation ensures longer life of the spindles as well as the ring and travellers. The following steps are taken for correct plumbing and setting –
a. That is stopped, twist gear disconnected, bobbins are removed and the spindle assembly (spindle blade, bolster cage and bolster insert) cleared from lint, thread etc.
b. Ring-rail is brought drawn to the bottom position.
c. The special bobbin that is provided with a circular collar having its diameter about 1/8 th inch less than the diameter of the ring; the upper surface of the collar should have white paint or some bright color which helps detections of the clearance between the collar and the ring easily is mounted for correct fitting of the spindle.
d. Then looked down directly over the top of the spindle and seen for uniform clearance by judging the intensity of light.
e. If the clearance is not uniform, the nut which holds the spindles, base is loosen slightly and the base is shifted by lapping gently with a wooden hammer to the correct centre position.
f. The ring-rail is raised to the top of the spindle and checked for uniform clearance.
g. If not, tilt the spindle for uniform clearance without disturbing the horizontal adjustment.
h. When the spindles are all plumbed, the thread guide is so adjusted that the contact point of the thread on the back side of the thread guide is strictly vertical on the centre of the top of the spindle blade.
This important operation should be done regularly under schedule to maintain proper spring conditions.
Tuesday, October 28, 2014
What are the factors to be considered for the selection of proper ring size? What are the advantages and disadvantages of large and small ring diameter?The selection of proper ring size depends on such prime factors as –
a. Spindle speed – Higher the spindle speed, smaller the ring dia.
b. Size of the bobbins – Larger the size of the bobbin, larger the ring dia.
c. Types of bobbin – Heavier and larger bobbins are adapted with larger ring size. Warp bobbins for larger ring size and weft for smaller ring size.
d. Warp and weft – Larger ring size for weft and smaller ring size for warp.
e. Yarn number – Higher the yarn number, lower the ring size.
f. Traverse of the thread board – Higher the traverse of the thread board, larger the sing size.
Larger ring size
a. Larger package and fewer knots which means better yarn quality.
b. Less cost of doffing, spooling, winding, reeling etc.
c. Favors higher lifts and therefore, larger yarn packages.
d. Easier manipulations for the operatives.
e. Favors the spinning of lower count yarn.
a. Larger gauge of frame. Hence, less spindles/frame and more floor space for more frames for a desired mill unit.
b. Higher initial capital investment for a desired mill unit.
c. Lower spindle speed, lower front roller speed and hence lower production.
d. Requires heavier traveller, hence greater frictional resistance causing more wearing out of the rings etc.
Smaller ring size
a. Favors higher spindle speed and higher front roller speed, hence higher production is possible.
b. Smaller gauge of frame means more spindle/frame, hence less floor space is required for a desired mill unit.
c. Less initial capital investment for a desired mill unit.
d. Requires lighter traveller, hence less frictional resistance causing less wearing out of the rings.
e. Favors the spinning of higher count of yarn.
a. Smaller yarn packages cause more knots, hence inferior yarn qualities.
b. More cost of doffing, spooling, winding, reeling etc.
c. Shorter lifts and therefore smaller yarn package.
d. Careful attention and manipulation for the operators for smaller gauge of the frame.