RINGS And TRAVELLERS - 4
Ratio bobbin length (H) : Inside ring diameter (D)
Thread tension increases with growing bobbin length. In view of the limited thread tension, the total bobbin length should not exceed 5 times the ring diameter. Only when using balloon control rings or similar devices this value can be exceeded.
H : D = 5 : 1
Ratio bobbin diameter (d) : Inside ring diameter (D)
The bobbin diameter d is equivalent to the mean outer bobbin diameter d 1 + d 2
The following values are recommended:
for spinning: d : D = 0.48 - 0.5 (a = 29°-30°), (minimum value a = 26°)
for twisting d : D = 0.44 - 0.5 (a = 27°-30°), (minimum value a = 22°)
For light and heavy bobbins, the values for light bobbin types are decisive for calculating d : D. If the ratio d : D is reduced thread tension increases.
Correct surface smoothness, i.e. optimum peak-to-valley height and evenness of the ring track
The traveller contact surfaces must be smooth and even. Only then a smooth operation of the traveller will be possible. The contacted surfaces should be clean and preferably without traces of wear. In addition, they should be designed in such a way that they offer sufficient adherence for potential lubricants (e.g. fibres, oil, grease).
Once the sliding surfaces have lost their original quality, even the best ring traveller will not be able to run smoothly. For maintaining the surface of the running track in a good condition, it is very important - besides a certain degree of maintenance - to run the ring well in.
Balloon control rings and separators
The influence of balloon control rings is quite considerable, especially at long cops. A reduction of the yarn balloon is advantageous or may even be the prerequisite for optimum performance. If balloon control rings are mounted at correct distance (the yarn balloon should be restricted as long as possibleduring one lift of the ring rail) then a marked performance increase is possible. The balloon control rings are removed when sensitive materials are processed and sufficiently long separators are installed to avoid many yarn breaks and to prevent fibre fly from accumulating on the adjacent spindles.
Traveller cleaners are an excellent method for removing all fibre fly that accumulates on the outer part of C and El travellers. The traveller cleaner should have the right distance to the outside ring flange. A distance of about 0.5 mm between cleaner and traveller (in operating position) is recommended. When adjusting the distance between outside ring flange and cleaner, the size of the traveller should be taken into consideration.
Constant temperature and air humidity have positive effects on the operation of the traveller. Changes of the room climate, such as raised air humidity will increase wear by friction. Besides the regular exchange of air, the purity of the air is of great importance for the traveller. Any dust (also dust from unsuitable floors) or other impurities may impair traveller operation and lead to more ring/traveller wear.
Flange width and ring height
Optimal operating results are reached when the ideal flange width is chosen for flange rings and the ideal ring height is obtained for self-lubricating HZ and J rings, dependent on yarn count range, yarn quality and traveller type.
Ring profile and traveller shape
Determining the most favourable ring and traveller shapes is a precondition for obtaining the optimal individual performance. If ring profile and traveller shape match well, the traveller will adopt a stable position in the ring. It should have sufficient tolerance of movement, so that any obstacles which may occur especially when the machine is started are avoided. A satisfactory large yarn clearance counteracts yarn breaks and yarn damage.
Running-in of rings
Normally the running-in procedure is decisive for the future positive/nega tive behaviour of the ring and the length of its service life. Every ring requires a certain degree of running-in time if it is to maintain high traveller speeds with as little ring and traveller wear as possible. During running-in the use of steel travellers without surface treatment is recommended. After the termination of the running-in process, steel travellers with surface treatment or nylon as well as bronze travellers can be used.
The running-in process, beginning with the starting phase, consists of improving the initial running properties of the metallic running surface up to the optimal values by smoothing and passivation(oxidation) as soon as possible. In this way, together with fibre lubrication, constant minimum mixed friction conditions and minimum thermal stressing can be attained for the ring traveller. A careful running-in process will improve the lifetime of the rings.
In order to keep the stress on the traveller as low as possible during the starting phase, it is advisable to always change the traveller in the upper third part of the cops. Further advantages are brought with the use of a traveller running-in program(reduction of the speed by about 10% for 10 to 20 minutes, only available on modern spinning machines).
Spindle speed should be reduced atleast for the first 10 traveller changes. If final speed is higher than 32m/sec, reduce by atleast 20%. If final speed is lower than 32m/sec, reduce by at least 10%.
New rings should not be degreased, but only rubbed over with a dry cloth.
In general, the running in should be done with the same traveller type which is used for normal operation with the 10 to 20% less than normal speed. It is not advisable to do running with the same speed but with 1to 2 numbers lighter travellers than usual.
The first traveller change should be carried out after 15 min
The second traveller chage should take place after 30 min
The third traveller change should be made after 1 to 1.5 hours.
The fourth traveller change should be made after the first doff.
Further traveller changes are to be made according to the manufacturers recommendations
HAIRINESS: Following are the reasons for higher yarn hairiness due to ring and travellers
Poorly centered spindles, anti balloon rings and yarn guides lead to inconsistent yarn tension.
Rough surfaces roughen the yarn(due to damaged parts)
Open anti balloon ring
The clearance between ring and cop should not be too small. Traveller will cut the fibres protruding from the cop.
the fibres get electrostatically charged
poor twist propagation to the spinning triangle due to lighter travellers
Heavy friction of the balloon on the anti-balloon ring respectively impact on the balloon separator( due to lighter traveller)
Poor ring centering
yarn getting roughened in narrow yarn passage in the traveller
scratched up yarn passages catch the yarn and roughen it (due to very high traveller running time)
friction of the yarn due to very high traveller weight
rough gliding surface of the ring ( due to worn out rings)
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