Q. What are the methods of fabric formation?

Ans. Weaving, knitting, non woven

Q. What is the principle of manufacturing woven fabric?

Ans. Weaving is the interlacing of two sets of (warp & weft) yarns at right angles in a prede-termined pattern.

Q. What is warp yarn (ends)?

Ans. Yarns that run lengths of the loom.

Q. What is weft yarn (picks)?

Ans. Yarns that are woven across the loom.

Q. What is the objective of warp preparation process?

Ans. To transfer yarns from cone packages to weaver’s beam

Q. What does beam preparation process consist of?

Ans. Creeling and warping

Q. What is creeling in warp preparation process?

Ans. Putting required number of yarn packages in the creels, in desired order, in order to make warper’s beam.Figure shows a creel.

Fig. A Creel

Q. How many types of creeling are done in warp preparation process?

Ans. Magazine creel, reversible creel, duplicate creel and truck creel.

Q. What are the types of warping systems?

Ans. Direct or beam warping,Indirect or sectional warping, andThread by thread warping

Q. What are warper’s beam and weaver’s beam?

Ans. Warper’s beam: A beam on which yarn is wound on the warping machine.

Weaver’s beam: A roller on which large flanges are usually fixed so that a warp may be wound on it in readinessfor weaving.

Fig. Magazine creel Fig. Reversible creel

Fig. Duplicate creel Fig. Truck creel

Q. What is direct or beam warping system?

Ans. The winding of the total number of warp ends in full width in a single operation from creeled bobbins,either onto a weaver’s beam, or on to a sectional beam.

For example;number of warp yarns = 3360creel capacity = 560Number of warp beams = totoal number of warp yarns/creel capacity

= 3360/560= 6

Q. What is indirect or sectional warping system?

Ans. In this warping system several sections are wound in sequence and parallel to each other on a drum.

Q. Describe the drop wire, heald eye and reed dent?

Ans. Drop wire is a metal piece that falls and hits anelectrode bar in case warp yarn breaks and stops theloom.

Heald eye is a part of heald through which each warpyarn is threaded. This allows the movement of eachwarp yarn to be controlled during weaving.

Reed dent is the opening in the reed. Reed beats thenewly laid weft yarns into the body of the cloth.

Fig. Drop wires

Fig. Heald frames and healds

Q. What is the reed count or reed number?

Ans. The number of dents per unit width of reed. Like:The number of dents per inchThe number of dents per 2 inchThe number of groups of 20 dents per 36 inchesThe number of dents per 10 cmThe recommended unit is dents/cm.

Q. What are primary motions?

Ans. Every loom requires three primary motions to produce woven fabric :

1. Shedding2. Picking3. Beating-up

Q. What are secondary motions?

Ans. 1. Let-off2. Take-up3. Weft selection

Q. What are ancillary motions?

Ans. 1. Warp stop motions2. Warp protectors3. Weft stop motions4. Weft relenishment

Q. What are warp protectors?

Ans. Warp protectors are only necessary in looms which use a free flying media to insert the weft, such as ashuttle or a projectline. They stop the loom before beat-up can occur if the media fails to be arrested in the correctposition after it has traversed the loom.

Q. What is drawing-in?

Ans. After preparation, the warp yarn is “drawn in” throughthe eyes of the heald mounted on the required shafts(harnesses).

Q. What are the four fundamental operations in weaving?

Ans. • Shedding• Picking• Beating up• Take up and let off

Q. What is shedding process?

Ans. It is a primary motion in weaving that does separation of warp threads, according to pattern, to allow forweft insertion or picking prior to beating. It is the mechanism that raises certain harnesses above the others.Yarns that pass through the heald eyes in those harnesses are raised above that are not controlled by the raisedharnesses. In this way, a sheet of warp yarns is up, and a sheet of yarns is down. The space between two yarnsheets is called “shed”.

Q. What are open shedding, semi open shedding and closed shedding methods?

Ans. Open shedding: It is a method of forming a shed in which,between the insertion of one weft pick and the next, the onlywarp threads moved are those that are required to change posi-tion from the upper to the lower line of the shed, or vice versa.

Semi open shedding: It is a method of forming a shed in whichthreads, which are to remain in the top shed line for the nextpick, are lowered a short distance and then raised again. Theother threads are raised and lowered as in open shedding.

Closed shedding: It is a method of forming a shed in which all warp threads are brought to the same level after theinsertion of each pick of weft. They are of two types i.e., bottom closed and centre closed sheddings. Thedifference between them is that the terms ‘bottom’ and ‘centre’ indicate the position of the warp threads when atrest.

Fig. Open-shedding

Fig. Semi Open-shedding

Fig. Bottom closed Fig. Centre closed

Q. What is picking (weft insertion)?

Ans. Picking is the second operation of the weaving process. After the shed has been formed, the length ofweft is inserted through the shed.

Q. What is beating up?

Ans. Beating-up is the third operation of the weaving cycle. As soon as a weft yarn is inserted, the reedpushes or beats-up the weft to the fell of the cloth.

Q. What is fell of the cloth?

Ans. The fell of the cloth is the edge which is nearest to the reed as the cloth is being woven. In other words,beating-up occurs when the reed pushes the newly inserted weft against the fell of the cloth (Refer fig.).

Q. What is temple?

Ans. It is a device used in weaving to hold fabric at the fell as near as possible to the width of the warp in thereed.

Q. What is let -off (warpcontrol) motion?

Ans. This is the motion which delivers warp to the weaving area at the required rate and at a suitable constanttension by unwinding it from a flanged tube known as the weaver’s beam.

Fig. Fell of the cloth and other important functions

Fig. Negative let-off motion

Q. What are positive and negative let -off (warp control) motions?

Ans. Positive let off motion: A mechanism controlling the rotation of the beam on a weaving or other fabricforming machine where the beam is driven mechanically.

Negative let off motion: A mechanism controlling the rotation of the beam on a weaving or other fabric formingmachine where the beam is pulled round by warp against a braking force applied to beam.

Q. What is take up (cloth control) motion?

Ans. This is the motion that withdraws fabric from the weaving area at a constant rate. It ensures that therequired pick spacing is maintained, and then winds it onto the cloth roller.

Q. What are positive take up and negative take up motions?

Ans. Positive take up motion: It is the motion in whichthe take up roller is gear driven, a change wheel orvariable-throw pawl and ratchet being provided to allowthe required rate to be obtained, so determining thepick spacing.

Fig. Position of sensing roller in an automatic positive let off motion

Fig. Positive take-up motion

Negative take up motion: It is the motion in which the take up roller is rotated by means of a weight or spring, thisroller only rotates when the force applied by the weight or spring is greater than the warp lay tension in the fabric.The take up rate is controlled by the size of the force applied by the weight or spring and/or the warp tension.

Q. What is leno weaving?

Ans. It is the form of weaving in which two adjacent warp yarns cross each other between the picks.

Q. What is woven terry fabric?

Ans. A warp pile fabric in which loops are created, without positive assistance, by varying the relative positionsof the fell and the reed. A high tension is applied to the ground warp and a very low tension to the pile warp.

Q. Show major systems of loom ?

Fig. Negative take-up motion

Fig. Major systems of loom

Ans.Q. How many types of shedding motions are available?

Ans. Tappet, dobby and jacquard

Q. What is tappet shedding system?

Ans. The tapping shedding system is a motion of tappets and cams that cause shafts to be raised to form theshed. The mechanical arrangement of this system occupies so much of space that it can accomodate maximumof eight shafts and that is why its eight shafts represent maximum size of its weave repeat. This limits to theweaving of plain weaves, simple twills and simple sateen and satin weaves. Incase, the repeat of the desireddesign require more than eight shafts, then a dobby loom has to be used. Fig. shows tappet shedding with rollerreversing.

Fig. Tappet shedding with roller reversing

Q. What is dobby shedding system?

Ans. A mechanism for controlling the heald shafts of a loom. It is required when the number of heald shafts or thenumber of picks in repeat of pattern or both are beyond the capacity of tappet shedding This is a shedding systemcapable of having upto 32 shafts. Being able to accomodate up to 32 shafts, a much greater weave repeat andcomplicated design is possible.

Q. What is jacquard shedding system?

Ans. This shedding system has no shafts. A harness consisting of as many cords as there are ends in the warpsheet connects each end individually to the Jacquard machine situated high above the loom. Therefore, each warpcan weave independently of all the others. Since each warp yarn can be controlled individually, the greatest weaverepeat is possible . This enables most intricate designs to be woven. Fig.1.1, 1.2, 1.3 and 1.4 show single liftjacquard shedding, double lift jacquard shedding, double lift jacquard shedding formation and electronic jacquardrespectively.

Fig.1.1 : Single lift jacquard shedding Fig.1.2 :Double lift jacquard shedding

Fig.1.3 : Double lift jacquard shedding formation

Fig.1.4 : Electronic jacquard

Fig. Shuttle system of weft insertion

Q. What are the types of looms?

Ans. Single shed loom: Shuttle loom: 1. Hand loom 2. Power loom

Shuttleless loom: 1. Projectile or gripper loom 2. Rapier loom 3. Air jet loom 4. Water jet loom

Q. Show the shuttle system of weft insertion ?

Ans.

Shuttle

Healds

Warp sheet

Q. Describe the projectile or gripper loom ?

Ans. A weaving machine in which the weftthread is gripped by jaw(s) fitted in aprojectile, which is then propelled throughthe shed. It has a small hook like devicethat grips the end of the filling yarn.

Q. Describe the rapier loom ?

Ans. Machines in which the means ofcarrying the weft through the shed is fixedin the end of a rigid rod or in a flexibleribbon, this being positively driven. A rapiermachine may have a single rapier to carrythe weft across the full width or a singlerapier operating bilaterally with a centrallylocated bilateral weft supply, or two rapiersoperatiing opposites sides of the machines.

Fig. Gripper shuttle (projectile) weaving

Rapier is a flexible steel tape, one end of which takes the filling yarn half the width of the fabric tothe centre of the shed where a second rapier picks up the yarn and takes it the remaining half ofthe fabric across the shed. Sometimes there is sysytem of single rapier that takes the filling yarnacross the fabric and then empty rapier returns back leaving the new filling yarn in place. Differentrapier systems are shown in figure.

Fig. Different rapier systems

Fig. Double rapier system

Q. Describe water jet loom?

Ans. In water jet loom, a water jet is propelled across the shed with the force, that takes the filling yarn to theother side.

Q. Describe the air jet loom ?

Ans. In air jet loom, a jet of air is projectedacross the shed with the force, that takesthe filling yarn to the other side.

Q. Describe the multiphase loom ?

Ans. The multiphase loom can form manydifferent sheds at different places, therebyenabling insertion of number of filling yarns,one behind the other.

Fig. Relay air-jet system

Q. What is selvedge?

Ans. Selvedge is the woven edge portion of a fabric parallel to the warp edge. It is a firmer construction thanrest of the fabric that provides neat edge and a secure grip for fininshing machines.

Usually the selvedge has an increased number of ends per inch. Selvedges may contain special effects or brandnames or fabric descriptions woven into them.

Q. What types of selvedges can be formed?

Ans. Tuck-in selvedgeDouble-pick interwoven selvedgeFused selvedgeHelical selvedgeInserted selvedgeLeno selvedgeTraditional selvedge

Q. How is tuck in selvedge formed?

Ans. Tuck-in selvedge is formed by tucking-in protruding portions of each pick into the next warp shed, alongsidethe new pick, and beating them up together with it.

Fig. Tuck selvedge

Q. How is leno selvedge obtained?

Ans. Leno selvedge is formed by one or more pairs of strong, highly tensioned ends that interface with the wefton the leno principle. Warp threads are crossed and interwoven into the edges of the fabric.

Q. How is fused selvedge formed?

Ans. Fused selvedge is the thermoplastic warp and weft that are welded together by heat and pressure.

Q. How is helical selvedge formed?

Ans. Helical selvedge is formed by nipping each pick between two strong, highly tensioned ends which interwinecontinuously, each end having a helical configuration.

Fig. Leno selvedge

Fig. Helical selvedge

Q. How is double-pick interwoven selvedge formed?

Ans. Double-pick interwoven selvedge is formed by interweaving a strong selvedge end with the legs of theprotruding loops, using a small reciprocating shuttle.

Q. How inserted selvedge is formed?

Ans. Inserted selvedgeis formed by inserting additional short double picks of strong fine yarn by means of areciprocating needle.

Q. How traditional selvedge is formed?

Ans. Traditional selvedge is formed without making special provision on a shuttle loom weaving plain cloth.

Q. What is the normal weight range of woven fabric?

Ans. Very heavy > 13 oz/yd2

Heavy > 6 - 13 oz/yd2

Medium > 4 - 6 oz/yd2

Light > 2 - 4 oz/yd2

Very light < 2 oz/yd2

Q. What is the normal width range of woven fabric?

Ans. Broadloom = 108” Medium or average = 45, 54, 60, 72” Narrow = 27 - 36” Very narrow = < 12”

Q. What is lappet weave?

Ans. This is the type of weave in which floating threads are carried on the surface of the fabric and introduced atintervals to form the patterns. The floats are not long and the patterns are usually geometric, i.e. zigzag stripes inwhite yarn on a coloured plain weave ground.

Q. What is magazine loom?

Ans. This is the type of automatic loom in which the loom takes the empty bobbin from the shuttle andautomatically relpaces it with a new, full bobbin into the same shuttle. This exchange is made without stoppingthe loom. In this case, the weaver is restricted to one shuttle and one colour warp yarn ( called battery type).Another new type can use four colours in the warp.

Q. What is narrow fabric?

Ans. This is the type of any textile fabric made by interlacing fibres or yarns which does not exceed 45 cm ( inthe U. K.) and does not exceed 30 cm ( in the U. S. A. and other counries). Narrow fabrics are characterised bythe edges, which are the essential feature.

Q. What is ribbon loom?

Ans. This is the type of loom used for making narrow fabrics.

Q. What is needle loom?

Ans. This is the type of shuttleless weaving machine in which the weft is drawn from a stationary supply andintroduced into the shed in the form of a double-pick by a weft inserter needle. The weft is retained at the oppositeselvedge by the action of knittting or by the introduction of a locking thread from a separate supply.

Q. What is novelty weave?

Ans. Any weave which varies or combines the basic weaves, plain, satin and twill.

Q. What is swivel loom?

Ans. This is the type of loom meant for narrow fabric such as ribbons and tapes, the picking being done by aspecial type of small shuttle controlled by a swivel.

Q. What is swivel weaving ?

Ans. A fabric in which figure is achieved by the introduction of additional weft threads into base fabric toproduce small clipped woven-in-spot effects. The figuring yarn is fed from a series of shuttles mounted over the topof the weaving surface.

Q. What is tablet weaving ?

Ans. It is a method of making woven plain or patterned narrow fabrics, where warp is controlled by tablets madeof thin, stiff material, e.g. cardboard, plastic, bone, etc. Tablets are usually about 5 to 10 cm square, althoughother shapes, e.g. triangles, hexagons, etc. are also used. Each tablet has a hole at each corner through the warpyarns are threaded. Rotating the tablets controls the rise and fall of the warp yarns.

Q. What is box loom ?

Ans. A loom having two or more shuttles used for weaving fabrics containing weft yarns different as to size,twist or colour.