In precision (spindle-driven) winding of a cone, what happens as the package diameter grows?

The wind ratio stays constant and the yarn lay angle to the package surface decreases

The wind ratio drifts steadily downward through simple fractions, so ribboning cannot be avoided

The wind ratio stays constant and the yarn lay angle to the package surface decreases

The yarn is driven by surface contact with the drum, so slippage between drum and package sets the speed

The traverse stroke is lengthened automatically in proportion to the package diameter

A mill has to warp 6,000 ends of one identical plain warp for a very long production run, and later a short run of a striped shirting whose colour order changes across the width. Which pairing of warping methods is the sound one?

Beam warping for the long plain run and sectional warping for the striped shirting

Sectional warping for the long plain run and beam warping for the striped shirting

Sectional warping for both, because it always runs faster than beam warping

Beam warping for the long plain run and sectional warping for the striped shirting

Beam warping for both, because colour order can be set on the sizing machine

Which of the following statements about sizing of warp yarns are correct?

Size add-on is expressed on the oven-dry mass of the unsized yarn

Sizing binds down protruding fibres and raises the abrasion resistance of the warp

Size add-on is expressed on the oven-dry mass of the unsized yarn

Sizing binds down protruding fibres and raises the abrasion resistance of the warp

Filament warps normally need a heavier size add-on than spun cotton warps

Starch is a synthetic polymer made from petroleum feedstock

In an open shed, compared with a closed shed, what is true when the next pick needs an end to stay in the same line as before?

The end does not move, so the heald travels less and the shed forms with gentler motion

The end is brought down to the closing level and raised again, doubling its movement

The end is moved to the mid level between the two lines so that it meets all the other ends there before the next pick

Open sheds can only be formed by a tappet motion and can never be formed by a dobby or a jacquard

The end does not move, so the heald travels less and the shed forms with gentler motion

A mill wants to weave 100% polyester filament yarn at very high speed with water as the weft-carrying medium. Which statement is correct?

A water-jet loom is suitable because the yarn is hydrophobic and does not swell or absorb the water

A water-jet loom is unsuitable because polyester absorbs a great deal of water and loses its strength

A water-jet loom needs a pirn in a shuttle to guide the jet across the shed

A water-jet loom needs no drying of the cloth when polyester is woven

A loom has a sley driven by a long connecting rod, so its motion is taken as simple harmonic with the same crank radius throughout. The loom speed is raised from 200 to 300 picks per minute with one pick per crank revolution. By what factor does the peak sley acceleration, and hence the peak sley inertia force, change?

2.25, because the peak acceleration ω² r scales with the square of the speed

1.5, because the inertia force of the sley is directly proportional to the loom speed

3.0, because the force is proportional to the cube of the speed ratio

2.25, because the peak acceleration ω² r scales with the square of the speed

1.0, because the stroke of the sley and the crank radius have not changed at all

On a loom with a ratchet take-up, a change-wheel is replaced so that the cloth advances farther per pick, the weft supply and loom speed being unchanged. What is the effect on the fabric?

The picks per cm fall, so the fabric becomes lighter and more open in the weft direction

The picks per cm rise, so the fabric becomes heavier per unit area

The picks per cm are unchanged, only the warp tension rises

The ends per cm fall, because the warp is drawn out of the reed

The picks per cm fall, so the fabric becomes lighter and more open in the weft direction

Which description fits a terry (towel) construction?

A tightly tensioned ground warp and a slack pile warp, the pile threads being pushed up the picks to form loops

Two separate cloths woven one above the other with their own warps and wefts, joined by stitching ends

One warp in which a doup end crosses over its neighbour between picks to lock the weft in an open structure

A single plain-woven cloth whose warp ends are all drawn through one and the same heald shaft

Which of the following statements about shuttleless weft insertion are correct?

An air-jet loom uses a main nozzle with relay nozzles along a profiled reed to carry the weft

A water-jet loom suits non-absorbent filament yarns rather than cotton

A projectile loom launches a gripper projectile that carries the weft end across the shed

An air-jet loom uses a main nozzle with relay nozzles along a profiled reed to carry the weft

A water-jet loom suits non-absorbent filament yarns rather than cotton

A projectile loom launches a gripper projectile that carries the weft end across the shed

A rapier loom must carry its weft on a pirn inside a shuttle

Which of the following statements about shedding and cams are correct?

For a 3/1 twill woven on a tappet loom the cam shaft turns at one quarter of the loom crank speed

Negative shedding moves a heald one way by a cam and returns it by a spring or lever

A jacquard can raise each warp end, or small group of ends, independently

For a 3/1 twill woven on a tappet loom the cam shaft turns at one quarter of the loom crank speed

Negative shedding moves a heald one way by a cam and returns it by a spring or lever

Positive shedding cannot be used on any dobby loom

A jacquard can raise each warp end, or small group of ends, independently

Weaving Preparation, Loom Motions, Shuttleless Weaving and Woven Constructions

This chapter answers the first part of Section XE9.3 of XE9 Textile Engineering and Fibre Science, “Fabric Manufacture, Structure and Properties”, in the Engineering Sciences (XE) paper. XE9 is one of the nine optional sections, any two of which a candidate chooses in the exam. The syllabus lines covered are: “Principles of winding processes; Classification of winding methods; Patterning mechanism; Yarn clearers and tensioners; Different systems of yarn splicing; Warping objectives and classification; … Different sizing systems; Sizing of spun and filament yarns; Drawing-in process; Principles of pirn winding. Primary and secondary motions of loom; Shedding motion; … Beat-up; Kinematics of sley; Loom timing diagram; Cam designing; … Take-up and Let-off motions; Warp and weft stop motions; Warp protection; Weft replenishment; … projectile, rapier, water-jet and air-jet; … multiphase and circular looms; Types of selvedges; Basic woven fabric constructions …; Drawing and lifting plans.” The chapter follows the yarn from package to cloth: winding, warping, sizing, drawing-in, the loom motions, shuttleless weft insertion, selvedges and weave plans. Its numericals are drum-winding speed, tappet-shaft speed, take-up picks per cm, sley velocity, size add-on, warp length and mass with crimp, shuttle energy and weft-insertion rate.

1. Winding and warping

Winding transfers yarn from spinning bobbins to a larger, fault-checked package (cone, cheese) that unwinds freely at high speed. Its jobs are to enlarge the package, to remove faults, and to build a package of the right density and shape. In drum-driven (random) winding the package rests on a grooved drum that drives it by surface contact and also traverses the yarn, so yarn speed is nearly the drum surface speed, V = π D n (D drum diameter, n drum rev/min), reduced by slippage. In precision (spindle-driven) winding the package is driven directly and the traverse is geared to it, so the wind ratio (package revolutions per double traverse) stays constant while the yarn lay angle falls as the package grows.

Patterning (ribboning) is the build-up of yarn in ridges when the wind ratio becomes an integer or a simple fraction, so that successive layers fall on the same tracks. It spoils unwinding and dye uptake. It occurs in drum winding because the package diameter, and hence the wind ratio, drifts through such values. The cure is a patterning (anti-ribbon) mechanism: a ribbon breaker that briefly lifts the package from the drum or modulates the drum speed, or a traverse whose stroke is varied. Precision winding avoids the drift but must choose a wind ratio away from critical values.

Tensioners (disc, gate, washer types) add a controlled drag so the package is firm. Clearers (mechanical slot, or electronic capacitive and optical) cut out thick places, slubs and foreign matter. Splicing rejoins the ends after a cut: compressed air untwists the two ends, overlaps them and retwists the fibres, giving a joint of nearly yarn diameter and strength, far better in weaving and knitting than a knot.

Warping arranges the required number of ends parallel and at uniform tension on a beam. Beam (direct) warping winds all ends from a creel onto several warper’s beams of equal length, later combined on the sizing machine: fast, for long runs of one warp. Sectional (pattern) warping winds the ends in narrow bands side by side on a drum and then transfers them to the weaver’s beam: slower, but it suits short runs and coloured stripe patterns. Creels (magazine, travelling, V-type) hold the supply packages.

⚠️ Count beams from the creel capacity

In beam warping the number of warper’s beams = total ends ÷ creel capacity (rounded up), and all beams must carry equal ends and equal length or the sized sheet is uneven. In sectional warping the same ratio gives the number of bands. Warp mass = ends × length (m) × tex ÷ 10⁶ kg (tex = g per km = mg per m).

2. Sizing, drawing-in and pirn winding

Warp yarns are rubbed thousands of times by heald eyes, reed and neighbours, so sizing coats them with a film-forming adhesive and lubricant. It binds down protruding fibres (hairiness), raises abrasion resistance and strength, and cuts breakages. Ingredients are an adhesive (starch and its derivatives, polyvinyl alcohol, CMC, acrylics), plus softeners or lubricants, and preservatives. The size is a processing aid and is removed later (desizing) before dyeing. Size add-on is the dry size mass on the yarn as a percentage of the oven-dry unsized yarn mass: add-on % = wet pick-up % × (solids concentration) ÷ 100 when pick-up is quoted on that same dry basis.

Sizing of spun and filament warps
Aspect	Spun yarn (cotton, blends)	Filament yarn
Main aim	Bind protruding fibre ends and add strength	Hold the filaments together and give a smooth, lubricated, anti-static film
Size amount	Substantial add-on	Much lower add-on
Typical machine	Multi-cylinder slasher, sheet of many beams	Often sectional or beam-to-beam sizing with gentle drying

Drawing-in passes each warp end through its heald eye and reed dent in the order set by the draft and the reed plan, by hand or automatic machine. When a new warp is to be run with the same weave, tying-in knots the new ends to the old ones instead. Pirn winding makes the weft package for a shuttle: yarn from a cone is wound on a small tapered pirn by a builder motion that lays conical layers of increasing length, giving a firm package which unwinds over the end without snarling. The shuttle’s limited pirn capacity is why weft replenishment is needed.

3. Primary motions: shedding, picking and beat-up; sley kinematics and loom timing

The primary motions are shedding (separating the warp into an upper and lower line), picking (inserting the weft) and beat-up (the reed pushes the pick into the fell). The secondary motions are take-up and let-off, and the auxiliary motions are stop motions, warp protection and weft replenishment. In negative shedding the heald is moved one way by the cam and returned by springs or a lever; in positive shedding both movements are driven. Tappet (cam) shedding suits plain and simple twills on a few shafts; dobby controls many shafts (pegs on lags or electronic selection); jacquard lifts ends individually through hooks and harness cords for large figured designs.

Types of shed: in a closed (bottom-closed) shed all ends meet at one level between picks and then separate; in a semi-open (centre-closed) shed ends meet at a mid level; in an open shed ends that must stay in the same line for the next pick do not move, so the heald travels less and runs more gently at speed, while the closed shed gives a cleaner, more reliably formed shed for fine yarn. A tappet cam is turned by the bottom shaft at a speed equal to loom rpm ÷ (number of picks in the weave repeat): half speed for plain, quarter speed for 3/1 twill, one-fifth for a 5-end satin. Its profile has a rise, a dwell at the top, a fall and a dwell at the bottom; the dwell lets the shuttle or weft carrier pass, and a smooth (for example simple-harmonic) rise and fall limits heald acceleration.

Picking with a shuttle gives the shuttle kinetic energy ½mv² by a sudden blow from the picker (cone-over or side-lever mechanism); the shuttle flies through the shed and is checked in the opposite box by a check strap or brake. Mean deceleration over a braking distance s is v²/(2s). Too strong a pick wastes power and wears parts; too weak a pick lets the shuttle trap in the shed. Beat-up is driven by a crank and connecting rod swinging the sley. With crank radius r and speed ω, the sley velocity is about v = ω r sin θ, where θ is the crank angle from the front-centre (beat-up) position, so the peak velocity is ω r and the peak acceleration ω² r (the simple-harmonic approximation, valid when the connecting rod is long). Doubling loom speed doubles peak velocity and quadruples peak acceleration, hence inertia force.

The loom timing diagram plots events against crank angle, with 0° at beat-up (sley at the fell). The sley is farthest back at 180°, the shed is widest near the back-centre, and the shuttle must cross while the shed is open and the sley is back. Flight time = (crank angle allowed ÷ 360°) × (60 ÷ rpm). Sley setting is the crank angle at which the shed closes (the warp lines cross) relative to beat-up. Closing the shed early gives a tighter, more fully closed warp at beat-up and a firmer, denser cloth, with more warp tension and more end breaks; closing late is gentler. The cam profile and the setting together decide warp tension and pick spacing.

⚠️ Peak velocity is not average velocity

A sley with stroke 2r moves 2r in half a revolution, so its mean speed is 2r × (2 × rpm/60) = 4 r rpm/60, while the peak speed ω r = 2π r rpm/60 is π/2 times larger. Read the question: peak, mean, and the crank-angle convention (0° at beat-up) all change the number.

4. Take-up, let-off, stop motions, warp protection and weft replenishment

Take-up draws the finished cloth forward by one pick-space per pick, so it sets the picks per cm. In a positive take-up a ratchet wheel advanced by one (or a few) teeth per pick drives the take-up roller through a gear train, so cloth advance per pick = π D ÷ (T × R), where D is the roller diameter, T the ratchet-wheel teeth and R the speed reduction from ratchet wheel to roller. Picks per cm = T R ÷ (π D) (D in cm). Changing a change-wheel changes R and so the pick density. Let-off releases warp from the beam at the rate the cloth is taken up and keeps warp tension constant as the beam empties. In negative let-off the pull of the warp turns the beam against a friction brake (a weighted rope or lever) that must be re-set as the beam diameter falls; in positive let-off a sensor measures warp tension and a drive turns the beam to hold it.

Warp stop motion: drop wires hang on the ends and fall when an end breaks, closing an electrical circuit (or tripping a mechanical bar) to stop the loom. Weft stop motion: a weft fork (side or centre) or an electronic feeler checks each pick and stops the loom if it is missing. Warp protection guards the warp when a shuttle is trapped in the shed: in a loose-reed system the reed can recede on contact and trips a knock-off, so the sley does not crush the warp. Weft replenishment changes the empty pirn without stopping the loom, either by transferring a fresh pirn into the running shuttle (pirn change) or by replacing the whole shuttle (shuttle change); shuttleless looms avoid it by drawing weft from large stationary packages.

5. Shuttleless weft insertion, multiphase and circular looms

Shuttleless looms insert a measured length of weft from a large stationary package, so there is no pirn, no pirn winding and no shuttle impact, and speed and width rise. Weft insertion rate (m/min) = picks per minute × reed width (m).

Principles of the four shuttleless systems
System	How weft is carried	Notes
Projectile	A small gripper projectile, launched by a torsion-bar blow, clamps the weft end and carries it across; a conveyor returns the projectile	One projectile per pick; wide fabrics, many yarn types
Rapier	Rigid rods or flexible tapes carry the weft from one side, or two rapiers meet at the centre and transfer it (loop or tip transfer)	Gentle on yarn; easy colour change
Water-jet	A pumped water jet from a nozzle drags the weft through the shed	Needs non-absorbent (hydrophobic) filament yarns; fabric must be dried
Air-jet	A main nozzle plus relay nozzles along a profiled reed blow the weft across on compressed air	Very high insertion rate; weft is metered from a feeder; high air consumption

Multiphase looms form several sheds along the warp at the same time, so several wefts are inserted simultaneously in a travelling-wave fashion and the effective insertion rate is multiplied. Circular looms weave tubular fabric, as for sacks and hoses: shuttles run round a ring-shaped shed formed in a circular warp, so no cutting or seaming of the tube is needed.

6. Selvedges, woven constructions, drawing and lifting plans

A selvedge is the self-finished edge that stops the weft ends from fraying. A shuttle loom makes an ordinary selvedge because the weft turns back at each edge. Shuttleless looms cut the weft, so they need a tucked-in selvedge (the cut ends are tucked back into the next shed by tucking needles or air), a leno selvedge (two ends twisted round the weft ends by a doup), or a fused selvedge for thermoplastic yarns. A fringe is left deliberately in some fabrics.

Basic woven constructions
Construction	Principle
Plain, twill, satin	Interlacing every pick; diagonal line with step 1; scattered intersections with long floats (a satin repeat of n ends needs n shafts and a move number coprime with n)
Crepe, cord	Irregular small interlacing for a pebbled surface; cord has warp-way or weft-way ribs made by grouping threads or floats
Terry	Two warps: a tight ground warp and a slack pile warp; pile loops form when the pile warp is pushed forward along the picks
Gauze, leno	A doup end crosses over its neighbour between picks, locking the weft in an open, slip-resistant structure
Double cloth	Two cloths woven one above the other with separate warps and wefts, joined by stitching ends or by interchanging layers

The design (weave diagram) shows the interlacing on squared paper. The draft (drawing-in plan) assigns each end to a shaft: straight, pointed or broken. The lifting plan (peg plan) states which shafts are raised on each pick, one row per pick of the repeat (these rows are the lags of a dobby). The reed plan gives ends per dent. The minimum number of shafts equals the number of different end-patterns in the repeat. A jacquard needs no draft: the number of hooks must cover the ends of one pattern repeat, and if each hook is tied to k ends, ends = hooks × k.

Key takeaways

Drum winding gives yarn speed ≈ π D n less slip; precision winding keeps wind ratio fixed. Ribboning arises at integer or simple-fraction wind ratios and is broken by a patterning mechanism. Splicing beats knotting; clearers remove faults.
Beam warping suits long runs, sectional warping suits patterns and short lots. Warp mass = ends × length × tex ÷ 10⁶ kg, with warp length = fabric length × (1 + crimp) for crimp on a fabric-length basis. Add-on = pick-up × solids concentration.
Negative shedding returns healds by springs; positive drives both ways. Tappet shaft speed = loom rpm ÷ picks per repeat. Dobby handles many shafts, jacquard individual ends. Open sheds move healds less than closed ones.
Sley motion is crank-and-rod, approximately simple harmonic: peak velocity ω r, peak acceleration ω² r; doubling speed quadruples the inertia force. Shuttle energy ½mv² is dissipated in the box over a braking distance s at mean deceleration v²/(2s).
Picks per cm = T R ÷ (π D) for a ratchet take-up; a bigger change-wheel advance gives fewer picks per cm. Negative let-off is friction-braked, positive let-off is tension-sensed. Weft is stopped by forks or feelers, the warp by drop wires.
Projectile, rapier, water-jet and air-jet insert weft from a stationary package; insertion rate = ppm × reed width. Shuttleless edges are tucked-in, leno or fused. A lifting plan lists shafts raised per pick; shafts needed = distinct end-patterns.

Practice questions (16)

Attempt each one before opening the answer. Every explanation names the tempting wrong option as well as the right one, because that is where marks are lost.

In precision (spindle-driven) winding of a cone, what happens as the package diameter grows?
1. The wind ratio drifts steadily downward through simple fractions, so ribboning cannot be avoided
2. The wind ratio stays constant and the yarn lay angle to the package surface decreases
3. The yarn is driven by surface contact with the drum, so slippage between drum and package sets the speed
4. The traverse stroke is lengthened automatically in proportion to the package diameter
Show answer
Answer: B — The wind ratio stays constant and the yarn lay angle to the package surface decreases
In precision winding the package spindle is driven and geared to the traverse, so package revolutions per double traverse (the wind ratio) are fixed; as the circumference grows, the same traverse advance per revolution makes a smaller lay angle. The drift of the wind ratio and the dependence on slippage describe drum-driven winding, which is the tempting wrong choice. The traverse stroke is not changed with diameter.
A mill has to warp 6,000 ends of one identical plain warp for a very long production run, and later a short run of a striped shirting whose colour order changes across the width. Which pairing of warping methods is the sound one?
1. Sectional warping for the long plain run and beam warping for the striped shirting
2. Sectional warping for both, because it always runs faster than beam warping
3. Beam warping for the long plain run and sectional warping for the striped shirting
4. Beam warping for both, because colour order can be set on the sizing machine
Show answer
Answer: C — Beam warping for the long plain run and sectional warping for the striped shirting
Beam warping is fast and economical for long runs of a single warp, while sectional warping lays ends in bands in any colour order, which suits short runs and stripes. The reverse pairing is wrong on both counts, and sectional warping is slower, not faster. Colour order cannot be created at the sizing machine, which only combines beams.
Which of the following statements about sizing of warp yarns are correct?
1. Size add-on is expressed on the oven-dry mass of the unsized yarn
2. Sizing binds down protruding fibres and raises the abrasion resistance of the warp
3. Filament warps normally need a heavier size add-on than spun cotton warps
4. Starch is a synthetic polymer made from petroleum feedstock
Show answer
Answer: A — Size add-on is expressed on the oven-dry mass of the unsized yarn; B — Sizing binds down protruding fibres and raises the abrasion resistance of the warp
Add-on is defined on dry unsized yarn, and the binding of hairiness and the gain in abrasion resistance are the purpose of sizing. Filament yarns have no protruding fibre ends, so they take a much lower add-on, not a higher one. Starch is a natural polymer from plants, not a petroleum-derived synthetic.
In an open shed, compared with a closed shed, what is true when the next pick needs an end to stay in the same line as before?
1. The end is brought down to the closing level and raised again, doubling its movement
2. The end is moved to the mid level between the two lines so that it meets all the other ends there before the next pick
3. Open sheds can only be formed by a tappet motion and can never be formed by a dobby or a jacquard
4. The end does not move, so the heald travels less and the shed forms with gentler motion
Show answer
Answer: D — The end does not move, so the heald travels less and the shed forms with gentler motion
In an open shed an end that is wanted in the same line for consecutive picks simply stays put, which reduces heald movement. Bringing the end down to the closing level and raising it again describes the closed shed, where all ends meet at one level between picks, and the mid-level meeting is the semi-open shed. Dobbies and jacquards are exactly the mechanisms that make open sheds easy.
A mill wants to weave 100% polyester filament yarn at very high speed with water as the weft-carrying medium. Which statement is correct?
1. A water-jet loom is suitable because the yarn is hydrophobic and does not swell or absorb the water
2. A water-jet loom is unsuitable because polyester absorbs a great deal of water and loses its strength
3. A water-jet loom needs a pirn in a shuttle to guide the jet across the shed
4. A water-jet loom needs no drying of the cloth when polyester is woven
Show answer
Answer: A — A water-jet loom is suitable because the yarn is hydrophobic and does not swell or absorb the water
Water-jet insertion works best with smooth, non-absorbent filament yarns such as polyester or nylon, because they neither swell nor take up the water. The claim that polyester absorbs a lot of water is wrong, and the cloth still carries surface water and is dried afterwards. Shuttleless looms have no shuttle and no pirn.
A loom has a sley driven by a long connecting rod, so its motion is taken as simple harmonic with the same crank radius throughout. The loom speed is raised from 200 to 300 picks per minute with one pick per crank revolution. By what factor does the peak sley acceleration, and hence the peak sley inertia force, change?
1. 1.5, because the inertia force of the sley is directly proportional to the loom speed
2. 3.0, because the force is proportional to the cube of the speed ratio
3. 2.25, because the peak acceleration ω² r scales with the square of the speed
4. 1.0, because the stroke of the sley and the crank radius have not changed at all
Show answer
Answer: C — 2.25, because the peak acceleration ω² r scales with the square of the speed
Peak acceleration is ω² r, and ω rises in the ratio 300/200 = 1.5, so the acceleration rises by 1.5² = 2.25 with r unchanged. A factor of 1.5 is the change in peak velocity, which is the tempting error. The stroke is unchanged, but acceleration depends on speed, not stroke alone.
On a loom with a ratchet take-up, a change-wheel is replaced so that the cloth advances farther per pick, the weft supply and loom speed being unchanged. What is the effect on the fabric?
1. The picks per cm rise, so the fabric becomes heavier per unit area
2. The picks per cm are unchanged, only the warp tension rises
3. The ends per cm fall, because the warp is drawn out of the reed
4. The picks per cm fall, so the fabric becomes lighter and more open in the weft direction
Show answer
Answer: D — The picks per cm fall, so the fabric becomes lighter and more open in the weft direction
Picks per cm equal the picks inserted per unit length of cloth drawn off, so a larger advance per pick spreads the same number of picks over more length and lowers the pick density. The weight per unit area falls, the opposite of the claim that picks per cm rise and the fabric gets heavier. Ends per cm is fixed by the reed and the warp width, not by take-up.
Which description fits a terry (towel) construction?
1. A tightly tensioned ground warp and a slack pile warp, the pile threads being pushed up the picks to form loops
2. Two separate cloths woven one above the other with their own warps and wefts, joined by stitching ends
3. One warp in which a doup end crosses over its neighbour between picks to lock the weft in an open structure
4. A single plain-woven cloth whose warp ends are all drawn through one and the same heald shaft
Show answer
Answer: A — A tightly tensioned ground warp and a slack pile warp, the pile threads being pushed up the picks to form loops
Terry needs two warp systems at different tensions, the slack pile warp forming loops when the picks are drawn together. Two cloths joined by stitching is double cloth, and the doup crossing is leno or gauze. A single heald shaft for all ends would give no shed at all.
A 5-end warp-faced satin is woven in which every end is raised over the weft on four of the five picks of the repeat and lowered on one. How many shafts are raised in each pick of its lifting plan, with a straight draft on five shafts?
1. 4 shafts
2. 1 shaft
3. 5 shafts
4. 2 shafts
Show answer
Answer: A — 4 shafts
Each end is down on exactly one pick of five, and the interlacings are spread so that one different end is down on each pick, so on every pick four of the five ends, hence four shafts, are raised. One shaft raised per pick would describe the weft-faced satin. Raising all five would give no interlacing at all.
Which of the following statements about shuttleless weft insertion are correct?
1. An air-jet loom uses a main nozzle with relay nozzles along a profiled reed to carry the weft
2. A water-jet loom suits non-absorbent filament yarns rather than cotton
3. A projectile loom launches a gripper projectile that carries the weft end across the shed
4. A rapier loom must carry its weft on a pirn inside a shuttle
Show answer
Answer: A — An air-jet loom uses a main nozzle with relay nozzles along a profiled reed to carry the weft; B — A water-jet loom suits non-absorbent filament yarns rather than cotton; C — A projectile loom launches a gripper projectile that carries the weft end across the shed
The air-jet, water-jet and projectile descriptions are the standard principles of those systems. A rapier loom takes weft from a large stationary package and carries it with rods or tapes, so it has neither a shuttle nor a pirn.
Which of the following statements about shedding and cams are correct?
1. For a 3/1 twill woven on a tappet loom the cam shaft turns at one quarter of the loom crank speed
2. Negative shedding moves a heald one way by a cam and returns it by a spring or lever
3. Positive shedding cannot be used on any dobby loom
4. A jacquard can raise each warp end, or small group of ends, independently
Show answer
Answer: A — For a 3/1 twill woven on a tappet loom the cam shaft turns at one quarter of the loom crank speed; B — Negative shedding moves a heald one way by a cam and returns it by a spring or lever; D — A jacquard can raise each warp end, or small group of ends, independently
The cam makes one turn per repeat, 4 picks here, so its speed is one quarter of the crank speed. Springs or levers return the heald in negative shedding, and a jacquard harness gives individual control. Dobbies are built with positive (two-way) drives, so the statement forbidding them is false.
A positive take-up has a ratchet wheel of 30 teeth advanced by one tooth per pick. The gear train gives a speed reduction R = 20 (the take-up roller turns once while the ratchet wheel turns 20 times). The effective roller diameter, including its covering, is 10.0 cm. Using picks per cm = T R ÷ (π D), the picks per cm, to one decimal place, is ____.
Numerical answer — type the value.
Show answer
Answer: 19.1
Roller turns per pick = 1 ÷ (T R) = 1 ÷ 600. Cloth advance per pick = π × 10.0 ÷ 600 = 0.05236 cm. Picks per cm = 1 ÷ 0.05236 = 600 ÷ (π × 10) = 19.10, so 19.1. Forgetting that R is a reduction, or using the radius instead of the diameter, gives answers off by 20 or by a factor of two.
A drum-driven winder has a grooved drum of diameter 10.0 cm turning at 1200 rev/min. Slippage between drum and package means the yarn is wound at 97% of the drum surface speed. The yarn winding speed, to the nearest whole number of m/min, is ____.
Numerical answer — type the value.
Show answer
Answer: 366
Drum surface speed = π D n = π × 0.100 m × 1200 = 376.99 m/min. Yarn speed = 0.97 × 376.99 = 365.68 m/min, which is 366 to the nearest whole number. Using the circumference as the diameter, or ignoring slippage (377), are the common slips.
The sley of a loom is driven by a crank of radius 60 mm making one revolution per pick at 220 picks/min. Taking the sley motion as simple harmonic, v = ω r sin θ, the peak sley velocity in m/s, to two decimal places, is ____.
Numerical answer — type the value.
Show answer
Answer: 1.38
ω = 2π × 220 ÷ 60 = 23.04 rad/s. Peak velocity = ω r = 23.04 × 0.060 = 1.382 m/s, so 1.38. Using the stroke 2r instead of r, or the mean speed 4 r rpm/60 = 0.88 m/s, would be wrong.
A fabric length of 100 m is to be woven with 3000 ends of 30 tex yarn. Warp crimp is 7%, defined as (yarn length − fabric length) ÷ fabric length. Ignoring size, waste and wastage at the ends, the mass of warp yarn needed, in kg to two decimal places, is ____. (tex = mg per m)
Numerical answer — type the value.
Show answer
Answer: 9.63
Yarn length per end = 100 × (1 + 0.07) = 107 m. Total length = 3000 × 107 = 321,000 m. Mass = 321,000 m × 30 mg/m = 9.63 × 10⁶ mg = 9.63 kg. Taking 100 m with no crimp gives 9.00 kg, which is the usual omission.
A sizing machine gives a wet pick-up of 82% (liquor mass taken up as a percentage of the oven-dry mass of the unsized yarn). The size liquor contains 9% solids by mass. The size add-on on the dry unsized yarn, in per cent to two decimal places, is ____.
Numerical answer — type the value.
Show answer
Answer: 7.38
Per 100 g of dry yarn the yarn takes up 82 g of liquor. Dry size solids = 0.09 × 82 = 7.38 g. Add-on = 7.38 ÷ 100 × 100 = 7.38%. The wet pick-up of 82% is not itself the add-on, because 91% of the liquor is water that is dried off.