Comber machines play a vital role in the textile spinning process, refining raw fibers to produce uniform, high-quality sliver for yarn production. Combing operation is carried out between carding and draw frame machine. It is primarily used in long-staple fiber processing (such as combed cotton yarn production) to remove short fibers, neps, and impurities, improving fiber parallelization and yarn quality.
Mechanical Faults in Comber Machine
Mechanical faults in the comber result in excessive variation in the quality of the web produced. It is, therefore, essential to check the machine settings and timings along with the condition of working parts and take corrective action. Besides, mechanical faults in a comber machine can cause inefficiencies, poor sliver quality, and machine breakdowns. Here are some common mechanical faults in comber machine:
1. Damage to Half-Lap and Top Comb:
Both the half-lap and top comb are very important parts in the comber and are considered the heart of the combing process. The saving in re-needling or repairing does more harm in the long run and hence the expenditure on these should be incurred as and when the needles are found damaged. Thus, cleaning of the half-lap or straightening of the bent needles should be done promptly. The double-end piecing of the lap normally leads to the development of sudden stresses on the needles. Hence the tenter should be trained for carrying out correct lap piecing of an old and a fresh lap. In the latest modern combers, automatic lap piecing is provided to eliminate the fault of double-end lap feeding. Along with this, it is essential to replace excessively worn-out brushes. This is because, as the bristles become shorter in length, they lose their flexibility. As a result, not only the cleaning of needles is affected but their rigidness also puts additional pressure on the needles. With new brushes, loading on the half-lap is easily avoided and at the same time, the possibility of needle damage is much reduced.
One of the reasons for the damage to the top comb is its faulty setting with detaching rollers. Too close a setting, makes the top comb touch the top roller surface occasionally. Here too, along with the needles, it also spoils the top roller covering. Further, when the top comb is allowed to enter the fringe too deeply, the resistance that its needles experience during detachment is likely to cause some damage to the needles.
2. Uneven and Inadequate Nipper Grip / Feed Roller Grip / Detaching Roller Grip:
It is very important to have the uniformity of nipper bite across its width and feed roller and detaching roller grip across their length. As for the nippers, this can be checked by inserting a thin paper strip between the two nippers.
When the nippers are closed, the paper should be evenly gripped when moved from one end to the other. The same also can be tried with a feed roller. This is because, both these are spring-loaded. In these cases, it is advisable to check the position and the condition of these springs. With insufficient nipper grip, there is a possibility of long fiber loss; whereas with inadequate feed roller grip, some uncombed portion of the lap fleece would be allowed to escape into the comber web.
The loading on the detaching roller is directly related to the efficiency with which detachment takes place. Inadequate pressure, especially on the back top detaching roller results in long fiber loss and also leads to back-end combing.
3. Curling of Fibers in the Web:
This is a typical defect that occurs when the already combed fiber fringe is withdrawn back for piecing. This fringe follows the curved surface of detaching rollers and hence leads to wild piecing.
The common reasons for such defects are: faulty detaching roller covers – either spoiled or not cleaned, too high or too low humidity and faulty passage of air currents generated by the aspirator i.e., the air entering the detaching zone and passing on further to the aspirator.
4. Holes in the Web:
These are mainly due to disturbances in the web caused by air leakages. A faulty setting between the air strip and the brush, leakages in the air seal or worn-out brush bristles – are the common reasons for this defect.
5. Uncombed Portion in the Web:
Some of the portions of the lap, without being properly exposed to the cylinder combing actions, escape to form the web. This usually occurs at the time of detaching fleece. Uneven laps, ineffective feed roller pressure and too wide setting of the feed roller from the nipper bite are common reasons.
6. Plucking:
This is commonly experienced with long staple fibers where the half-lap needles enter the fringe with sudden impact carrying away the long fibers. The probable reasons are – variation in the lap weight – along and across the length, poor fiber parallelization, ineffective nipper grip, rusty-rough or bent needles on the half-lap.
7. Cutting Across:
In the web, thin and thick places appear regularly; so the web appears to be cut at these places. The fault may be due to bad laps prepared at the lap machine, incorrect roller settings, excessive drafts or roller slip. With incorrect timing of detaching cam, the faulty piecing of the web can also result in thin–thick places appearing at regular intervals.
Wrong position of the top comb – too deep placement of comb into the web and/or very close distance of comb from the detaching roller also lead to its excessive interference during detachment and cut in the web.
8. Web Not Coming through Heads:
During the normal working of the comber, it is sometimes observed that there is no web or sliver coming from one or more heads. At times, the lap at the back gets exhausted or there is lapping around detaching rollers. Both can be detected by a vigilant worker and the time lost in repairing the damage to the product can be kept to a minimum.
However, in some cases, it is necessary to observe whether there is excessive fiber loss on any of the heads where most of the fibers are taken away by the cylinder. This may be due to the ineffective bite of the nippers, foreign matter wedged in between the nipper bites or even a faulty detaching roller. In the last case, the detaching rollers are required to be lubricated to ensure their smooth running. In some other cases, the pawl engaging the feed ratchet gets disengaged or the ratchet itself becomes loose. This stops the feed to the corresponding comber head.
9. Lap Running Slack between Lap Roller and Feed Roller:
This is basically due to improper co-ordination in speeds of lap and feed rollers. Either the former is feeding excess of lap or the latter is taking a little less. Even, as stated earlier, the pawl on the feed roller may be disengaged or the feed roller ratchet may have become loose on its shaft.
10. Lapping on Detaching Rollers:
The defect is mainly due to wrong atmospheric conditions (higher Relative Humidity, R.H.) or bad condition of detaching roller covers. In the second case – oil on the roller cots, badly worn-out cots requiring varnishing, dirt sticking on the cots and hence requiring cleaning or improper roller clearers – are some common reasons.
11. Flocking of Waste on Cylinder Needles:
One of the important operations after combing by cylinder is the stripping of cylinder needles by the revolving brush. But owing to several reasons, this is not done effectively and efficiently. One or more brushes get loose on the shaft or sometimes uneven wearing-out of the brush bristles results in a gap between the bristles and the cylinder needles.
The air leakage through the aspirator is yet another problem which reduces the strength of the suction. The deposition of fibers on the brush continues, but the waste on the bristles is not drawn by the suction from the aspirator. Hence, the respective brush loaded with fiber noil is no longer able to strip the cylinder needles. As for the suction, the function of the air strip placed over the brush is very important. The air suction controls the effectiveness of the stripping action. If the brushes are well cleaned by the suction they, in turn, strip the needles efficiently. On some modern Rieter combers, ‘a slow motion’ for the cylinder is provided at intervals, wherein except the brush shaft, all other parts are made to periodically run at slow speed. This allows a regular and efficient cleaning of needles.
When the cylinder needling (half-lap or UniComb) is found damaged, the waste frequently gets accumulated on and around this damaged portion. This leads to the flocking of waste.
12. Excessive Loss of Long Fibers:
During the working of the comber, it is important to carefully observe, from time to time, the nature and the feel of the noil collected on the aspirator drum. When the noil contains excessive whitish long fiber tufts, they are easily noticeable. Even the Baer sorter diagram of the noil taken in such cases can easily reveal this. Improper nipper bite has a direct influence over the loss of long fibers during combing. Sometimes, a foreign matter gets wedged between the nipper jaws. This invariably leads to uneven gripping of the lap fringe. Even the irregular lap across the width leads to the same result. Bad covering of detaching roller leads to ineffective gripping of fibers during detachment of the fiber fringe. The damaged needles of the top comb or its wrong setting increase its interference. This causes serious disturbances during the detachment of the fiber fringe. The longer fibers are unnecessarily withheld by such disturbances and fail to pass on to the detaching rollers. In the subsequent combing cycle, these fibers are simply removed during the cylinder combing operation.
13. Irregular Draw-Box Sliver:
Normally, owing to the piecing wave, the comber head sliver becomes irregular and weak. However, apart from this, head-to-head variation in the noil, also results in non-uniformity in the hank of sliver delivered on the sliver table.
When the head sliver passes over the sliver table, there is always some rubbing over the table surface. It is here that the slivers are very likely to experience ‘false draft’ (non-intended draft) if the table surface is slightly rough. The tension draft between – (a) the table calender roller and detaching roller and (b) the back draw-box roller and table calender roller – have to be within limits. This is because the distances at these two controlling zones are much wider than the effective length. Any stretching in these two zones directly leads to irregular table slivers. The breakages of sliver/s occurring in the above two regions lead to a defect – ‘singles and doubles’. If the worker minding the machine is not alert, these are normally not attended to immediately. This again leads to irregularity in the draw-box sliver.
The bad condition of the detaching roller covering, improper settings and weightings in the draw-box can all aggravate the situation. The use of an ordinary drafting system (conventional 4/4 drafting) leads to the ‘phasing’ of the piecing wave. Many comber manufacturers, with their new high-speed models, have introduced modern drafting systems such as 3/5 or 4/5. In some spinning mills, the conventional drafting system is modified as 2/2 or 3/3 drafting with an improved weighting system on top rollers. However, the amount of drafts that can be introduced in such cases is limited. It may be noted here that this draft in the comber draw-box is not employed to improve orientation and parallelization. This is because the fibers in the comber sliver already attain a good deal of both of these qualities, again due to cylinder needle and top comb needle action. In some combers, the head slivers are divided into a group of four and bi-coiling is used. In this case, the draft involved for each sliver group is only around four. In a Within comber a 4/5 system is used; whereas, in Rieter’s E-86 comber, a 3/3 system is employed.
Conclusion:
Comber machine, critical in textile spinning for enhancing fiber quality, can encounter various mechanical faults affecting performance and output. By addressing these mechanical faults proactively, comber machines can maintain high fiber quality and operational efficiency in textile production.
References:
[1] Khare, A. R. (2023). Principles of spinning: Combing in Spinning. CRC Press.
[2] Kumar, R. S. (2014). Process management in spinning. CRC Press.
[3] Purushothama, B. (2011). A practical guide to quality management in spinning. In Woodhead Publishing Limited eBooks. https://doi.org/10.1533/9780857093950
[4] Purushothama, B. (2012). Training and development of technical staff in the textile industry. In Woodhead Publishing Limited eBooks. https://doi.org/10.1533/9780857095848
[5] Purushothama, B. (2016a). Handbook on cotton spinning industry. CRC Press.
[6] Kiron, M. I. (2021c, October 31). Problems / Defects / Faults of Combing Process with Causes and Remedies. Textile Learner. https://textilelearner.net/problems-in-combing-process/
