Presentation on theme: "Process Control in Weaving Shri R. P. Tewari International Polytechnic for Women, New Delhi."— Presentation transcript:
Process Control in Weaving Shri R. P. Tewari International Polytechnic for Women, New Delhi
Steps Involved During Weaving Operation Selection of yarn for warp and weft purposes Sizing Winding - Spool winding (for warp) -Pirn winding (for weft) Preparatory Processes for Sectional Warping -Creeling -Hecking -Denting in section guide reed -Leasing Warping on horizontal drum warping machine Beaming Drafting arrangement Denting Gait-up the loom Tie up the loom Weaving
Selection of Yarn for Warp and Weft Purposes Proper selection of yarn by the technical supervisor at the institution for warp and weft. Clear instructions to the weaver (Material handling, faults etc) Job instruction sheet for a particular design should be provided.
Sizing Objectives -To reduce the end breakage rate by improving the abrasion resistance and also the tensile strength of the yarn. -To enhance the weavability. Precautions Use of digital balance. Add cold water to the sizing agent. Sequence of size preparation -Mixing the adhesive component of size with cold water. -Addition of wetting agent to the adhesive component. -Mixing the lubricating agent with boiling water and then adding it to the mixture of sizing and adhesive component. -Addition of antiseptic agent to the above.
-Boiling all the mixed ingredients on slow fire with continuous stirring. -Continuation of boiling till the sizing paste becomes transparent and of constant viscosity. It is checked by lifting the liquor with the help of a stick. -The paste is then cooled with continuous stir. -It is then filtered through fine muslin fabric. -The boiled and filtered paste is diluted with cold water to the required volume as per the liquor to material ratio of 10:1.
Confirmation of the readiness of the size paste Lift the size paste between the thumb and the forefinger and smudge it for some time. Separate out the two fingers. Tackiness should be felt while separating the fingers. Take small amount of size paste and spread it on a clean glass. Allow it to dry. A formation of thin film on drying indicates the good preparation of the size paste. The absence of tackiness and film formation indicates that the size paste is not properly prepared.
Hank preparation for Sizing Wetting (use of wetting agent-TRO), Washing and Cleaning. Conformation of proper wetting Over and under-squeezing of hanks should be avoided. Use of hank shaker for squeezing.
Sizing operation Use of rectangular sizing tank in stead of round pot. Use of cross bars to hang the hanks for sizing. Squeeze the sized hank by using hank shaker. Over and under-squeezing should be avoided. Drying of sized hank Drying under direct sunlight should be avoided. Avoid spreading the hank on the floor. Change the position of hanks time to time. Avoid over and under drying of the hanks. Give jerks by both the hands to prevent entanglement. Do not store the sized hanks one over another. Hang in a wooden sticks.
WINDING Spool Winding (For warp) Locate the first and the last end of the hank. Proper use of swift stand. During winding the thread should come out from the top side of the swift. Location of swift and spool should be parallel and right direction with respect to each other. The threads should be uniformly distributed in the spool and the bobbin should be tightly wound. The filled bobbin should be stocked one over the other in a rectangular container in vertical position.
Clockwise unwinding of hank from swift Swift Warp Bobbin (Spool)
Pirn Winding (For Weft) Proper selection of pirn. Pirns should be clean and empty. The metallic portion of the pirn (head & nose) should be rust free. Knotting of the thread to the pirn should be avoided. Pirns should be uniformly and tightly filled up. The broken ends should be joined by piecing. Knotting should be avoided. Over filling of pirn should be avoided. Last weft end of the pirn should be crossed around the filled pirn (Fig)
Sectional drum warping Preparatory processes a) Creeling -The end of the thread from each bobbin should be released from the top. -In order to prevent the entanglement of the broken ends of the thread tie a strong cord in tight condition on the center of each section vertically. -Use of over filled warp bobbin should be avoided. -All the filled bobbins should be of equal weight and size.
b) Hecking -The threads of the creel should be divided in odd and even series (all the odd numbered threads should be drawn in to the eye of the heck heald and all the even numbered threads should be drawn in to the dent of the heck). c) Denting in section guide reed -Denting in reed (threading) should be according to the weave pattern so that the total width of the warp in the warp beam should tally to the width of warp in the actual weaving reed. d) Selection of appropriate counting device e) Leasing -Use of leasing reed for cross formation. -Insertion of the two lease cord in to the section should be formed after half metre distance.
Warping -Tension of all the ends in each section must be uniform and constant at the time of withdrawal from the supply package. Use tension device. -Spools should be properly aligned in the creel. -Maintain the proper sequence of ends by aligning the spool in the creel. - Routine checking of any interruption in the path of warp ends between creel to section guide.
-Cleaning of complete warping set at regular intervals. -Tension of all sections should be moderate. -Too soft or too tight warping should be avoided. -Warp beam along with its flanges should be carefully handled. -The yarn should not be subjected to sharp abrasive action to avoid the size removal. -Spreading of the yarn throughout the whole width of warping must be as uniform as possible. -Predetermined length of warping should be strictly observed for every section, beam, ball or journey of mill warping, as the case may be.
Beaming - The width of the warp ends in the warp beam should be equal to the width of the reed. The flanges should be fitted at right angles to the beam surface and it should be fitted at the center in equal distance from both side end of the beam. -Use of warp beam apron is essential.
Drafting If a new type of fabric is to be woven, calculate the total number of heald shafts required. The total number of heald eyes required in each heald frame should be calculated according to design patern. All the frames should be parallel to each other. Filled warp beam should be fitted just over the heald shafts. Proper selection of heald hook required as per the need of the heald gauge. A heald hook is shown below.
Denting -Appropriate reed count should be selected according to the yarn count and the total number of ends per centimeter. -The denting order should be according to the design pattern. -The surplus portion of the reed should be equally divided in both the sides. -Use of reed hook as shown below is required instead of heald hook.
Gait-Up the Loom -Warp beam should be accurately fitted in to the brackets. -All the heald shafts should be joined with the shedding device (rollers/pulleys/jacks etc) so that their tops are in a straight line horizontally. -Reed should be properly fitted to the grooves (sley groove and reed cap groove) -The bottom and the top of the reed should completely sink in to the grooves in horizontal position. -The reed grooves and reed cap grooves should not be too wide or too narrow. Otherwise it will bend to either side. -Discard the use of too old, damaged or rusted reed.
Tie-Up the Loom -Each section of the warp should be parallel and with equal tension. -Each section should tie-up just parallel to the reed to the cloth beam. -In lieu of the section-tying rod, apron should be used. -According to the design pattern, required number of paddles should be accurately fitted at the middle of the loom width. -Required number of lamb rods should be accurately fitted below parallel to the heald frames. -All connections (with the paddles, lamb rod and shedding device) should be accurately tied up. -Everywhere, only slipknots should be used.
Shedding Appropriate shedding device should be selected. -Connecting cords for the shed formation should be even and strong. -The cords should not be directly linked with the heald shafts. In lieu of this the use of loop cord is suggested through which the connecting cord should pass and should be tied by slip knot to either side of the heald shaft. -Connecting cord from the central bottom of the heald shaft to the paddle should also be tied by slip knot to the loop cord. -Before weaving it is important to check the formation of uniform shed. Instead of using two heald shafts use four heald shafts.
The defective shed formation may be due to: Incorrect selection of heald wires such as length and gauge; Imbalance connection\on of connecting cords; Wrong drafting of the warp threads; Damaged healds; Broken ends of warp; Use of undesirable high count of reed; Uneven tension of the warp threads; Improper fitting of back rest; Improper fitting of the reed in to the grooves of the sley; Imbalance level of the shuttle rest board; Undesirable distance of lease rods; Uneven pressure through the paddle; and Improper selection of the shuttle
PICKING Picking should be uniform. Too early and too late picking should be avoided. All connections of the picking cord should be well balanced The picking cord should be even and strong The picking handle should be comfortable. Direct connection of picking cord to the picker should be avoided. In lieu of this the use of loop cord with picker is suggested. For proper picking the loom width should be according to the width of the fabric to be woven. The length of the reed should be equal to the distance between sley arms and the reed should be fitted parallel to the sley arms. For even picking proper selection of shuttle is necessary. The weft thread pirn should not be too tight or too loose.
The pirn dimensions (length and circumference) should be such that the pirn is properly fitted in to the shuttle. Shuttle board (Shuttle race) should be smooth and even. Shuttle holder should be properly fitted to the picker. It should not too narrow, too high or too thin. The use of proper shuttle eyelets is necessary for getting desired pick supply. The use of fur in the inner wall of shuttle is necessary for every fine and smooth weft thread. The knots in weft thread should be as minimum as possible.
Beating-up Uniform beating force should be applied. The beating should be in right angle to the fabric. In this regard it is necessary that the distance of both side- hanging noses of the sley should be in equal distance from the cloth guide roller. Trembling force should be avoided. The beater should be held centrally during beating. Far shed beating should be avoided. Open shed beating should be avoided. In lieu of this cross pick beating is suggested. The weaver should hold the sley cap from the center while giving beating force to the fabric.
Let-off Motion Too much or too little release of the warp threads should be avoided. The release of warp threads should be uniform. The tension on warp threads should be uniform. The let off motion device should be in both sides of the warp beam. The arrangement should be such that the let off motion operates automatically. The let off and take up motions should match with each other. Leasing rods should function smoothly.
Take-up motion Winding of the woven fabric should not be too tight or too loose. After weaving the winding of the fabric should be carried out at regular intervals. Take up motion device should be easily approachable to the weaver. If too tight fabric is to be woven, the use of tooth wheels for both take up motions and let off mechanisms necessary. Otherwise, for normal weaving the use of weight system is most appropriate.
Use and Function of Temple To maintain a constant width of the fabric parallel to the warp threads.
Checking the Loom for Errors The mistakes are: -A missed heald eye -A missed warp yarn. -Crossed drafted and dented threads -Too many yarns either in a heald eye or in a dent reed. -Missing dents of the reed.
Selection of Shuttle Select shuttles taking in to account the weave pattern, count of warp and weft, loom make and reed width. Avoid the use too old shuttle. Avoid the use of shuttle made of fibrous wood. Avoid the use of blurred and bended nose shuttles. The tongue of the shuttle should tightly grip the pirn. Shuttle eye should not project outside. It should be within the grip of the wood. The center of gravity of the shuttle should be towards the shuttle eye. It can be checked by holding the shuttle nose across the grip of the two forefingers. So that it tilts towards the shuttle eye let.
Maintenance and care of each part of machine etc.