Combing Process of Cotton: For getting high quality of yarn, one extra process is introduced which is called combing process. To remove short fibers, neps and impurities from sliver combing operation is done. In either words, the combing process is carried out in order to improve the quality of the sliver coming out of the card. Cotton fibers have a distribution of fiber lengths ranging from the longest fiber group to the shortest fiber group. Short fibers of length less than 12.5 mm do not contribute to the mechanical properties of the yarn but increase yarn hairiness, which adversely affects the yarn and fabric appearance. For these reason combing operation done for fine and strong yarn. Combed sliver has a better luster compared with carded sliver because of the improved fiber alignment.
The combing process is especially of value with longer cotton where the extreme variation in fiber length is too high for the best spinning conditions. The combing process is normally used to produce smoother, finer, stronger, and more uniform yarns. Combing has been utilized for upgrading the quality of medium staple fibers. The removal of short fibers in combing facilitates the better binding of long fibers in the yarn, which ensures greater strength.
Objects of Combing Process of Cotton:
The main objectives of combing are as follows:
Noil removal: To remove short fibers, neps and impurities by combing.
Equalizing: To improve evenness of the sliver by doubling.
Parallelizing: To create parallel arrangement of fibers in the sliver by drafting.
Blending: To compensate the raw material variations by doubling.
Dust removal: To remove dust within the overall process by suction.
Sliver formation: To make sliver and coil in a can by condensing and calendering.
Combing is done in order to increase the mean length of fibers.
Maximum possible elimination of short fibers can be well performed due to combing.
Luster property of the fiber is slightly increased.
Parts of Comber Machine:
The various parts of a comber machine are given in Figure.
Fig: Different parts of a comber machine
Combing Process of Cotton Fiber:
Receiving the cotton sliver from cards.
Preparing suitable laps for feeding to combers by combining multiple slivers and rolling them on a spool. For this a process of Sliver-lap and Ribbon-lap or Drawing and Super-lap may be used.
Feeding the laps to the combers.
Nipping the lap, combing and removing short fibres and hooks.
Piecing the combed web and making a continuous sliver.
Collecting the removed short fibers (comber noils) and sending to waste department for further action.
Providing the combed sliver cans to next process, i.e. draw frame.
Periodic cleaning and setting of machines to get the required quality of combing.
Control Points and Check Points of Comber:
It is essential to have clarity on the points to be controlled to achieve the targets and those to be checked to ensure the process in control. These points need to be reviewed from time to time and modified to suit the requirements of individual companies and their targets. Each mill should prepare its own “Control Points and Check Points” and display them in the work area so that the people on spot refer and follow.
Fig: Material flow through comber
Control Points / Setting Points in Combing: The setting between the machine elements in the comber machine plays a critical role in deciding the quality as well as processability of the material. The setting of machine elements influences the amount of waste removal and life of the machine elements. Good combing performance combined with higher production is possible with optimum and accurate setting between machine elements.
Selection of process parameters, viz. hank of feeding lap, type of half-laps, speeds, settings, drafts and delivery hank, percentage of noil to be extracted, type of feed to be employed, length of feed per nip, maximum fiber length accepted in noil, etc.
Deciding and maintaining the schedules for preventive maintenance like half-lap mounting, setting, brush mounting, buffing, etc.
Engaging trained workmen.
Maintaining the required temperature and humidity.
Designing and providing safety gadgets.
Deciding and following suitable color codification and channelization.
Deciding the work allocation for employees.
Deciding frequency and systems for waste evacuation and their disposal and implementing them.
Check Points in Combing:
Material related:
The mixing and hanks of lap fed and the plan.
Quality of laps fed; good quality without licking problem.
Machine related:
Condition of the machines, for example, gripping by nipper, surface of detaching rollers, pressure on detaching rollers and on drafting rollers, smoothness of sliver table, condition of trumpets.
Whether half-lap points are sharp and clean?
Working of stop motions.
The surface of detaching rollers and drafting rollers.
Condition of bristles on the brush roller.
Setting related:
The settings done and the specified.
The wheels put and the requirement.
Size and quality of the trumpets.
Performance related:
The noils extracted and the norms.
Head to head variation in noil%.
The hank of sliver produced and the plan.
Check whether the sliver is uniform and U% is within norms.
Whether the quality of web is good without piecing marks?
Increase in mean length of sliver.
Whether the breakages are in control and what are the reasons for breaks?
The production obtained and the targets.
The neps removal efficiency and the requirement.
Whether the neps in sliver are within control?
Documentation related:
The machines worked in the shift on different mixings and hanks.
Machine wise production in hanks and kilogram.
Machine wise noil collected in case of manual collection system.
Total noil collected in shift in case of automatic noil extraction.
Work practice related:
Removing of the noils in time.
Tenters carrying out the work as specified.
Whether the machines and the materials are labelled properly for identification?
Quality of the cans and springs used.
Removing of the wastes from spring bottom before feeding to machines.
Maintaining the temperature and humidity as per requirement.
Log book related:
Instructions for changing mixings and hanks.
Stoppages with reasons and actions taken.
Report on working in the shift.
M.I.S. related:
Machine number
Mixing
Hanks
Production in kilograms – Derived from hanks produced
Noil removed
Men employed
General:
Housekeeping.
Color codification practiced.
Stock of laps and combed materials.
References:
Handbook on Cotton Spinning Industry by B. Purushothama
Process Management in Spinning by R. Senthil Kumar
Textile Engineering-An Introduction Edited by Yasir Nawab
Mechanics and Calculations of Textile Machinery by B. Varadarajan, C. B. Senthil Kumar, and N Gokarneshan
Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. He is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.
