Saturday, October 19, 2019
WARP TYING OR KNOTTING:, A WEAVING PROCESS, MANUAL WARP PIECING, AUTOMATIC WARP TYING OR KNOTTING:
WARP TYING OR KNOTTING PROCESS:
The process of warp tying or knotting can we performed in two ways:
• Manual warp piecing.
• Automatic warp tying or knotting.
MANUAL WARP PIECING:
In this method of warp piecing, all the actions of process are performed manually. A well trained person does this job. Very high skilled is required to perform this job. When the existing warp beam is exhausted, this warp beam is required to change with new warp beam. First of all, the lease is inserted in the warp sheet of loom before unloading the empty warp beam. The empty warp beam is unloaded from the loom and new beam is loaded on the loom. Now piecer makes the temporary piecing stand with the help of aluminium pipes and wooden blocks. The warp sheet of new warp beam is passed over the aluminium pipe. The ends of leases of new warp sheet and warp sheet of loom are tied on the both side of the temporary piecing stand. The piecer stands between whip roller and aluminium pipe. He takes a bunch of each of warp end from the both warp sheet from one side of the machine. Now the piecer ties these bunches on his waist. He selects one end of new warp beam and one end of warp sheet of loom by hand. He cut the both end as per requirement with the help of a sharp knife. Now both the ends are twisted together to make a joint. This action is repeated again and again till completion of piecing. The lease helps to separate the ends in correct sequence and prevents crossing of ends to each other.
DISADVANTAGES OF MANUAL PIECING:
Manual piecing has many disadvantages, which are given below:
• Manual piecing is highly time consuming process.
• The end’s joints are not too strong, the twisted joints are opened during pieced warp pulling.
• The warp tension is not equal at both side of warp sheet after piecing.
• High end breakage occurs due to uneven warp tension when loom is restarted.
• Loom efficiency is reduced.
• Extra person may be needed to draw broken ends.
• There may be chances of wrong drawing or wrong denting.
• There may be pattern mistakes in the warp.
• High end breakage during pieced warp pulling can cause the end crossing.
AUTOMATIC WARP TYING OR KNOTTING:
The warp tying or knotting machine is very important machine in the weaving shed, when a style or fabric design is repeated for long time on a loom. When the design is repeated, fresh drawing-in of warp is not required. The ends of new warp beam are joined with the ends of warp sheet of the loom with the help of automatic warp tying or knotting machine.
The warp knotting is completed in two following steps:
DRESSING OF WARP SHEET:
The empty beam is unloaded from loom and is replaced with new warp beam. Now knotter sets the knotting stand behind the loom. First of all, the warp sheet of new beam is taken over the knotting stand then the ends are spread out on the stand. A brush roller holds the warp sheet temporarily. Now the lease rods are inserted into the warp sheet and the ends are tightened by rotating brush roller. When all the ends of warp sheet get tension properly, the tail of warp sheet is clamped by clamping stripes. Now knotter separates all the ends with the help of dressing brush. The brush roller is rotated after each ends separation. The process of ends separation is repeated till completion of proper end separation. Now the ends of warp sheet are brought on their proper place with the help of half reed (comb). When all the ends get their proper places, the warp sheet is fixed on the stand with the help of sheet fixing clamp. Now the lease rods are replaces by harness strings and these are tied on the both ends of the stand.
Now knotter takes the warp sheet of loom over the stand and same process is repeated as mentioned above. Now dressing process of warp sheet is completed and knotter starts next step which is called knotting.
Knotter mounts the knotting machine on the stand. he fixes the machine by locking the gears with toothed rack. Now the lease strings are passed through lease pipe and are tied on the right side of stand. The power supply of knotting machine is connected to the supply point. Knotter starts the machine by pushing start button. The machine automatically joins the ends of both warp sheets.
Structure and working of knotting:
The common components and working of knotting machine are given below:
An electric motor is mounted inside the machine. Toothed pulley is mounted on the motor rotter shaft. The motion is transmitted to the mechanism by a toothed belt. It is a D. C. motor. 180 volt A.C. supply is used to run this motor. A voltage stabilizer is used to supply constant voltage to the motor. This A.C. supply is converted into D.C. automatically by voltage convertor in the machine.
All the functions of knotting machine is controlled electronically. The speed of machine is increased or decreased by rotating a knob mounted on the top of the machine. If machine fails to select the end of top or bottom layer, feelers send a signal to the control unit and stops immediately. Start, stop and inching push buttons are mounted on the top of control unit card. All the machine operations are initialized by these push button.
A knots counter is mounted on the top of the machine, which counts the number of knots completed during the process.
Machine travelling gears:
These gears are mounted in the bottom of machine. When the knotting machine is kept over the stand, these gears are engaged with toothed rack of stand by pressing the gear locks. When the lock is pressed, the travelling gear comes downward and is engaged with teeth of rack. The toothed rack is fixed. When the machine becomes start, the gears also rotates. The machine travels on the rack with the help of rotating gears on toothed rack.
It is very important part of the knotting machine. Two needles of same size are used during process. Main function of selection needle is to select single end from each layer of warp sheet. Top needle makes selection of ends of top warp layer and bottom needle makes selection of ends of bottom warp layer. These selection needles are needed to change when warp count changes. Different number of selection needles are put in reserve according to various types of warp counts to be used.
The function of feeler is to send the confirmation of selection of ends to be knotted. If proper selection is not performed, the control unit stops the machine immediately. In the knotting machine, two feelers are used, one for bottom layer and other for top layer. These feelers moves by pressure of yarn.
The main function of yarn carrier is to carry the selected ends in between the yarn grippers. When selection process happens, the top selection needle pushes the end downward and bottom selection needle pushes the end upward. At the same time yarn carrier starts to move toward the yarn grippers. The top and bottom hook of yarn carrier catch the selected ends and carry them into the yarn grippers.
The main function of yarn grippers is to hold the selected ends during knotting. Two grippers are used in the knotting machine. Top gripper holds the end of top layer and bottom gripper holds the end of bottom layer. The pushing springs are used to create enough gripping pressure between the gripping plates of yarn gripper. The gripping pressure can be adjusted with the help of a screw. There is need to change gripping pressure when warp count is changed.
The function of main cutter is to cut the tails of end after the gripping the ends by gripper. There are two cutters used in the knotting machine. These cutters works positively. Top cutter cuts the tail of top end and bottom cutter cuts the bottom end.
When the extra length of both the ends are cut, the knotter hook start to rotate. It wraps both the ends together with it and makes a loop.
Knotting needle: The knotting needle is fitted in the hollow pipe of knotter hook. It makes in and out movement during operation. When the loop is formed, the needle comes out and catches the ends. Now the knot is completed.
When the knotting is completed, knotted ends have extra tail length. It is very difficult to pass these knotted ends through the eye of heald wire and dent of reed. It needs to cut extra length of tail. The waste cutter performs this job.
The lease pipes are used to select the ends according to sequence. The lease pipe makes up and down movement and separate the ends according to sequence.
PRECAUTIONS OF KNOTTING PROCESS:
Knotting or tying is very delicate process. Any negligence in the process may be dangerous in weaving. Following precautions should be taken during the process:
• The dressing of the both warp sheets should be done perfectly.
• All the ends should have enough and equal tension.
• There should be no crossing ends when the warp sheet is being clamped.
• Each warp layer should be clamped properly. There should not be any slippage between clamp and yarn.
• The tension on the warp sheet should be according to requirement.
• The length of tail of knotted ends should be adjusted properly by adjusting main cutter.
• The knot should be fully tight to prevent its slippage. If knot is loose, the length of knotting needle should be adjusted by making slight band in it.
• The gripping pressure should be adjusted properly.
• The edges of the main cutter should be enough sharp to cut the ends.
• The selection needle should choose precisely. Incorrect selection may cause of double selection of ends or selection failure.
• The waste cutter should work properly. Improper working of it may cause to break the ends.
• The quality of knots should be checked manually after regular interval of time.
• Cutting action of main cutter should be clean. If there is any fibrous part at the tail of end, it may be caught by grippers.
• Yarn feelers should work properly.
• Machine should be cleaned by kerosene oil. Machine should be run in a tub filled with kerosene oil for half hour.
• The oiling of machine should be properly. For oiling of machine, it should be run in the tub filled with sewing machine oil (22 number oil) for half hour.
• Machine should be cleaned with compressed air before knotting each time.
• Moving parts of dressing stand should be oiled properly.
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