Ariful Haque Ashik
Lecturer, Dept. of Textile Machinery Design & Maintenance
Bangladesh University of Textiles (BUTEX)
Corresponding email —firstname.lastname@example.org
One of the most frequently asked question is why do we slash? And the obvious answer is that we slash in order to apply size materials to the warp yarn. Another less obvious reason for slashing is to produce a yarn package for the loom by combining section beams that contain the correct number of ends for the fabric construction to be woven. If we do not size ,we could use a beamer to combine the section beams to contend with and would realize a significant savings by not sizing our yarn. We would have no dry cans to contend with and would realize a still further savings on steam cost. These may sound appealing but the reality is that most yarns cannot be woven without size.
For many yarns, the application of size improves breaking strength, but even more importantly, abrasion resistance is significantly improved. Abrasion resistance is a significant consideration for good weaving performance. With the application of size, we lay down some protruding fibers into the yarn bundle. This anchoring of fibers maintains the integrity of the fiber bundle as it is exposed to the various stresses of the weaving operation.
Another important function of the size is to lubricate the yarn surface to protect it from the abrasive forces of loom contact points during the weaving process.
A typical sizing formulation might contain polyvinyl alcohol corn starch, a binder, wax, and /or other lubricants, an anti-stat and a de-foamer.
The Slasher Departmental Manager’s responsibility is to prepare the sizing recipe as economically as possible, also the operator’s duty is to supervise that the warp is properly sized and free of defects.
One of the most critical duties of the slasher operator is the proper loading of a set of yarn actually begins with the running out of the old set of yarn. As he approaches set run out, the operator should observe section beams in the creel very closely not only to ensure that all yarn from this set is used, but also to further ensure that one or more beams do not run out of ahead of the entire group, a situation that would result in a warp with too few ends being sent to weaving. Once he has reached this point, he should identify, in some manner, a point where the first quality yarn ends and where questionable yarn begins, wash off his rubber rolls, raise the rubber rolls, and turn off steam to the size boxed; without wasting time, he should pull his good yarn over to the front of the slasher and doff his loom beam. It is undesirable to leave this yarn on the hot dry cans for an extended period of time during the loading process. He is now ready to start the loading process, his size boxes should be filled with water and allowed to boil while the new beams are placed in the creel. It is especially important that size boxes be thoroughly cleaned when PVA sizing formulations are used. Routine maintenance functions should be performed while the set is off, and this is also a very good time to examine rubber squeeze rolls, yarn guide rolls, etc. for any damage that might have occurred. In addition, most slashing managers schedule certain cleaning functions in and around the slasher while the set is off.
It is important that the leasing function be performed as specified by the management. One of the more common mistakes we see in slashing is the assumption by the operator that the set of yarn is running well and he does not need to lease. Omitting this function results in excessive stuck and crossed ends in your warps going to the weaving department.
We will now discuss some situations which we have encountered in slashing operations and some suggestions for confirming and/or correcting these situations.
High volume in the cooking kettle and low solids : A possible cause for these conditions is a water meter error from adding too much water to begin the cook. Another could be a water meter leak with the correct amount of water being charged but water gradually leaking in during the cooking process. Most cooking kettles are equipped with a high sheer circulating pump to assist in the cooking process. These are equipped with a water cooled bearing and a defective seal can result in water getting into the size solution, thereby causing dilution. Excessive condensate in the steam supply could also be a cause for this problem.
- Another situation could be volume of the finished cook low but solids high: This could be a water meter error with tool little water being charged for the cook.
- Another situation might be volume low, solids correct. Some possible caused would be a valve leaking size to the drain or a defective valve allowing raw size to pass to storage from the circulating pump during the cooking cycle.
- Volume could be slightly high with high solids. Possible causes for this could be excessive size added to the cook by operating personnel or an error weighing by bulk handling equipment.
- with the volume slightly low and solids low. A possible cause could be size omitted from the cook.
- Solids could be correct at the cooking kettle but low at the storage kettle. The most likely cause for this would be a leak in the closed steam coil in the storage kettle. This can be checked by emptying the kettle, drawing enough water into the kettle to cover the coil, turning on the steam and checking for bubbles.
- Solids could be correct at the cooking and storage kettles and be low at the size box. A likely cause for this could be condensate in the steam supply .We would suggest that steam traps be checked for proper operation.
In summarizing our narration, we would like to suggest that managers and supervisors spend some time with new operators. Explain to him why we size yarn. Show him some bad warps, not necessarily his, and explain why they are bad. Show him some good warps and explain why they are good.