Weaving

In short

Weaving is the interlacement of two sets of yarns at right angles — warp (lengthwise, on the loom beam) and weft or filling (crosswise, inserted pick by pick) — to produce a woven fabric. It is the largest fabric-forming route in India: shirting, denim, suiting, sarees, terry towels, home textiles and most technical fabrics are woven. The topic carries heavy weightage in university "Fabric Manufacture / Weaving Technology" papers and in GATE Textile Engineering and Fibre Science (TF), where loom motions, production and efficiency calculations, and weave design are regular questions. Interviewers at Arvind, Vardhman, Raymond, Welspun, Trident, KPR, Nahar, Loyal and at machinery suppliers (Picanol, Toyota, Tsudakoma, Itema) ask loom mechanics, picks-per-minute productivity and fabric-fault diagnosis.

Explained

Weaving preparatory (what must happen before a loom can run)

• Winding: transfers ring-frame cops onto large cones, removing objectionable faults with an electronic yarn clearer and splicing the ends (knotless joint) — gives long, fault-free lengths for warping.
• Warping: winds thousands of ends in parallel at uniform tension. Direct (beam) warping for grey, single-colour warps; sectional (indirect) warping for striped/checked and small-lot warps, where sections are built on a drum and transferred to the beam.
• Sizing: the single most critical step — a film-forming polymer (modified starch, PVA, CMC, acrylic) plus softener, wax and antistatic is applied to improve abrasion resistance, lay the hairiness and raise strength. Key variables: size add-on %, viscosity, squeeze pressure, stretch and moisture (usually left at 6–8%).
• Drawing-in and denting: each end is drawn through a drop wire (warp-stop), a heald eye on the chosen shaft (as per the drafting plan) and a reed dent (denting order, commonly 2 ends/dent); done on an automatic drawing-in machine or by hand/reaching.
• Pirn winding (shuttle looms only) and knotting/tying-in (a new beam is tied to the old warp on a tying machine to save re-drawing).
• Weft for shuttleless looms is fed directly from cones through a weft accumulator/feeder that pre-measures each pick length.

The loom and its motions

• Primary motions (fabric cannot form without them):
  1. Shedding — separating the warp into two layers to form a tunnel (the shed).
  2. Picking — propelling the weft through the shed.
  3. Beat-up — the reed, carried on the sley, pushes the newly laid pick to the cloth fell.
• Secondary motions (continuity of weaving): take-up (draws the woven cloth forward and so fixes picks per cm) and let-off (releases warp from the beam at near-constant tension; negative, semi-positive or electronically controlled).
• Auxiliary (stop/safety) motions: warp-stop motion (drop wires/electrical), weft-stop (weft feeler or photocell), temples (hold cloth to full width at the fell), brake, loose-reed or fast-reed warp-protector motion and shuttle-guard on shuttle looms.
• Main shaft (crankshaft) runs at loom speed; the bottom/cam shaft runs at half speed in a plain loom, but it carries two tappets, so a shed change still occurs on every pick (every crank revolution); for an n-pick weave the tappet shaft is geared to 1/n of crankshaft speed.

Shedding, picking and beat-up in detail

• Shed types: bottom-closed, centre-closed and open shed (healds move only as much as the next pick demands — least warp strain, used on modern dobbies). Shed geometry: front shed and back shed; a clear shed is essential for trouble-free weft passage.
• Shedding mechanisms by pattern capacity:
  • Tappet/cam — up to about 8 (sometimes 14) shafts, cheap, fixed small repeats: plain, twill, satin.
  • Dobby — about 16–30 shafts, pattern from pegged lags or an electronic file; large pick repeats.
  • Jacquard — each end (or small group) controlled individually through harness cords and heald hooks; figured designs, sarees, brocades, labels, terry borders. Electronic jacquards use solenoids instead of punched cards.
• Picking systems:
  • Shuttle (conventional): cone-over-pick or side-lever under-pick drives a shuttle carrying a pirn. Weft is continuous with the selvedge; 150–220 ppm; heavy, noisy, high energy per metre.
  • Projectile (gripper/Sulzer): a small gripper seizes the yarn tip, is launched by a torsion-bar, and is returned by a conveyor; very wide and heavy fabrics.
  • Rapier: rigid or flexible, single or double rapier (give-and-take at centre); 400–700 ppm; best for coarse, fancy and multi-colour wefts.
  • Air-jet: main nozzle plus relay nozzles in a profiled reed; fastest (700–1,500+ ppm) but high compressed-air cost and limited to fairly uniform wefts.
  • Water-jet: cheapest insertion for hydrophobic filament (polyester, nylon); fabric leaves wet.
  • Multiphase (weaving-rotor): several sheds and several picks in progress simultaneously — very high weft insertion rate, limited to simple weaves.
• Shuttleless looms cut the weft each pick, so the fabric needs a tuck-in, leno or thermal-fused selvedge instead of the self-selvedge of a shuttle loom.
• Beat-up force rises as the sley reaches front centre; cloth fell position and warp tension control starting marks (a fine weft bar when the loom restarts) — modern looms add a pick-finding and automatic fell-adjust routine.

Weave structures and design

• A weave is shown on point/design paper: filled square = warp up (warp float), blank = weft up. A complete repeat needs the design, drafting plan (which end on which shaft) and lifting/peg plan.
• Plain weave (1/1): maximum interlacements, firmest, most abrasion-resistant, repeat 2×2 — shirting, poplin, voile, sheeting. Variants by thread spacing and count: rib (warp rib 2/2, weft rib), matt/hopsack (2/2 basket).
• Twill: diagonal lines; notation 2/1, 3/1, 2/2 with a move number. Types: warp-faced (3/1 denim), weft-faced, balanced (2/2 gabardine), pointed/herringbone, broken, zigzag, diamond, elongated, curved twill. Fewer interlacements than plain → softer, better drape, more cover, more prone to slippage.
• Satin/sateen: longest floats, lustrous, repeat ≥5 with a selected move number coprime with the repeat (for 5-end: 2 or 3; move 1 and repeat−1 are invalid as they give twill). Satin = warp-faced, sateen = weft-faced.
• Derived and special weaves: honeycomb, huck-a-back (towelling), mock leno, crepe, bedford cord, welt/piqué, extra warp/weft figuring, backed and double cloth, terry (3-pick/4-pick pile with slack-warp loose pick beat-up), leno/gauze (doup heald crossing ends — mosquito net, scrim), velvet/velveteen (cut pile), gauze and jacquard brocade for Banarasi and Kanjeevaram work.
• Firmness rules of thumb: interlacement count ↑ → strength and cover ↑, but maximum achievable thread density ↓ (plain weave jams first; a 5-end satin can hold far more ends per cm).

Fabric parameters, faults and standards

• Specification of a woven fabric = warp count × weft count / EPI × PPI, width, weave, GSM, finish. Example: 40s × 40s / 120 × 60, 147 cm, plain, 112 GSM.
• Crimp (take-up) arises because the yarn path is wavy; warp crimp usually 5–12%, weft crimp 4–8%. It governs beam length, reed width and fabric weight.
• Cover factor (Peirce) measures how much of the fabric plane the yarns occupy; cloth cover maximum is 28 in the Ne/inch system.
• Common woven faults and causes: reed mark (bent/choked dent), starting mark (warp tension/fell shift at restart), weft bar (count or twist variation), double pick, missing end/float, broken pick, temple mark, oil stain, selvedge defects, shuttle/weft-fly mark, cracks from a wrong lifting plan. Inspection uses the 4-point system (points per 100 square yards, ASTM D5430; sometimes converted to points per 100 m²) in export houses.
• Indian test standards (BIS): conditioning in the tropical standard atmosphere, 27 ± 2 °C and 65 ± 2 % RH (IS 6359) — note ISO 139 uses 20 °C, so Indian results are quoted against the Indian atmosphere; threads per unit length (IS 1963), mass per unit area (IS 1964), tensile strength and elongation by strip method (IS 1969 Part 1), tear strength, dimensional change on washing. BIS revises and withdraws numbers periodically — verify the current edition before quoting it in a test report.
• Regulatory/industrial context: BIS Quality Control Orders now cover several textile items; GST on most fabrics and made-ups sits in the lower slabs of the 5%/18%/40% structure in force since 22 September 2025 (the exact rate is item-specific — check the current notification). Machine guarding, noise and working-hour compliance in a weaving shed now fall under the four Labour Codes in force from 21 November 2025, which replaced the Factories Act, 1948 and the Minimum Wages, Industrial Disputes and BOCW Acts.
• Indian industry structure: a very large decentralised powerloom sector (Bhiwandi, Malegaon, Ichalkaranji, Erode, Surat, Panipat) alongside modern shuttleless composite mills; handloom clusters protected under the Handlooms (Reservation of Articles for Production) Act, 1985. Modernisation is supported through the Amended Technology Upgradation Fund Scheme (ATUFS) and the PM MITRA mega textile parks; capacity and scheme status change, so quote current Ministry of Textiles data rather than a remembered figure.

Key points

• Weaving — interlacement of warp and weft at right angles on a loom.
• Primary motions — shedding, picking, beat-up; without any one of them no cloth forms.
• Secondary motions — take-up (fixes PPI) and let-off (holds warp tension).
• Auxiliary motions — warp stop, weft stop, warp protector, temples, brake: they protect fabric and machine, not formation.
• Sizing — adds abrasion resistance and strength to the warp; add-on typically 6–14% depending on count and loom type.
• Sectional warping — for coloured/striped and short-run warps; direct warping for long single-colour runs.
• Shed types — bottom-closed, centre-closed, open shed (open shed strains warp least).
• Tappet / dobby / jacquard — increasing pattern capacity: ~8 shafts / ~16–30 shafts / individual end control.
• Shuttleless advantage — higher speed, lower noise and vibration, automatic pick-finding, no pirn winding; needs an artificial selvedge.
• Air-jet — highest speed, high compressed-air energy; rapier — most versatile for coarse and multicolour weft; water-jet — hydrophobic filaments only.
• Weft insertion rate (m/min) — rpm × reed width; the true productivity comparator between looms of different widths.
• Plain weave — most interlacements, firmest; satin — longest floats, highest lustre and highest achievable density.
• Twill angle — 45° when EPI = PPI (move number 1); steeper when EPI > PPI.
• Satin move number — must be coprime with the repeat and not 1 or (repeat − 1).
• Crimp % — straightened yarn length over fabric length, minus one; decides beam length and GSM.
• Cover factor — thread density ÷ √count; maximum cloth cover 28 in the English system.
• Loom efficiency — actual picks inserted ÷ picks possible at rated speed; 80–95% on modern looms, lower on plain powerlooms.
• Starting mark — the classic restart fault; controlled by fell-position correction and warp tension control.

Formulas and examples

Example 1 — Production of an air-jet and a rapier loom (8-hour shift). Fabric 20 picks/cm, efficiency 85%.

• Air-jet at 700 ppm: picks = 700 × 480 × 0.85 = 285,600 → length = 285,600 ÷ (20 × 100) = 142.8 m/shift.
• Rapier at 450 ppm: picks = 450 × 480 × 0.85 = 183,600 → 91.8 m/shift.
• Shuttle loom at 180 ppm, η 80%: picks = 180 × 480 × 0.80 = 69,120 → 34.6 m/shift. The air-jet does the work of about 4.1 shuttle looms.

Example 2 — Loom efficiency from actual output. A loom rated 600 ppm produced 130 m of 20 picks/cm fabric in 8 hours.

• Actual picks = 130 × 100 × 20 = 260,000. Possible picks = 600 × 480 = 288,000.
• η = 260,000 ÷ 288,000 = 90.3%.

Example 3 — GSM of a shirting from its specification. 40s × 40s / 120 × 60, warp crimp 8%, weft crimp 6%.

• tex = 590.5 ÷ 40 = 14.76 tex for both.
• ends/m = 120 × 39.37 = 4,724; with crimp, yarn length = 4,724 × 1.08 = 5,101.9 m → warp mass = 5,101.9 × 14.76/1000 = 75.3 g.
• picks/m = 60 × 39.37 = 2,362; with crimp = 2,362 × 1.06 = 2,503.7 m → weft mass = 2,503.7 × 14.76/1000 = 36.9 g.
• Fabric = 112.2 g/m² (≈112 GSM) — a typical fine shirting.

Example 4 — Cover factor of the same fabric.

• K1 = 120 ÷ √40 = 120 ÷ 6.3246 = 18.97; K2 = 60 ÷ 6.3246 = 9.49.
• Cloth cover = 18.97 + 9.49 − (18.97 × 9.49)/28 = 28.46 − 6.43 = 22.03 out of a maximum 28 → a fairly closely set but weavable plain fabric.

Example 5 — Beam length, ends and reed for a weaving order. Order: 1,000 m of the above fabric, 150 cm finished-on-loom width, 2 ends per dent, weft crimp 6%, warp crimp 8%, loom + tying waste 25 m.

• Total ends = 150 × (120 ÷ 2.54) = 150 × 47.24 = 7,086 ends (plus selvedge ends).
• Beam length = 1,000 × 1.08 + 25 = 1,105 m.
• Reed width = 150 × 1.06 = 159 cm = 62.6 inch → ends/inch in reed = 7,086 ÷ 62.6 = 113.2 → dents/inch = 56.6 → reed count ≈ 113 (Stockport, dents per 2 inch).
• Warp yarn required = 7,086 × 1,105 m = 7.83 × 10⁶ m × 14.76 g/1000 m ≈ 115.6 kg before sizing; at 10% size add-on the sized beam weighs ≈ 127 kg.

Where it is used

• Composite and shuttleless weaving mills — Arvind and Raymond (denim, suiting), Vardhman and Nahar (shirting), KPR and Loyal, Welspun and Trident (terry towels, bed linen) running air-jet and rapier looms with electronic dobbies and jacquards.
• Decentralised powerloom clusters — Bhiwandi, Ichalkaranji, Malegaon, Surat (polyester saree and dress material), Erode and Somanur (cotton grey), Panipat (home textiles).
• Handloom and heritage weaving — Banarasi, Kanjeevaram, Paithani, Pochampally and Chanderi, using jacquard and extra-warp figuring; articles reserved for handloom production under the 1985 Act.
• Technical textiles — woven geotextiles, conveyor-belt and tyre fabric, airbag and parachute fabric, filter cloth, FIBC/woven sacks (tape looms), glass-fibre fabric for composites; large Indian base in Ahmedabad, Vadodara, Coimbatore and Surat.
• Job roles — weaving shift-in-charge, loom-shed maintenance and loom-setting engineer, fabric designer / CAD-CAM (dobby and jacquard files), quality-assurance and 4-point inspection, process improvement (loom efficiency, snarl and stop analysis), machinery sales and service (Picanol, Toyota, Tsudakoma, Itema, Lakshmi group).
• Exams and recruitment — GATE TF, university fabric-manufacture papers, NTC/SIMA/TAI diploma assessments, campus tests of spinning-weaving mills and export houses.

Interview questions

• Q: Name the primary, secondary and auxiliary motions of a loom. A: Primary — shedding, picking, beat-up; secondary — take-up and let-off; auxiliary — warp stop, weft stop, warp protector, temples and brake.
• Q: Which motion decides picks per cm in the fabric? A: The take-up motion, because it fixes how far the cloth advances between successive beat-ups; the loom speed does not change PPI.
• Q: Why is the warp sized but not the weft? A: The warp is held under tension and abraded repeatedly by healds, reed and beat-up; the weft is inserted once and faces almost no abrasion.
• Q: Why does a shuttleless loom need a tuck-in or leno selvedge? A: Each pick is cut after insertion, so there is no continuous weft turning back at the edge to form a self-selvedge.
• Q: Compare air-jet and rapier looms. A: Air-jet is faster and better for uniform, plain fabrics but costs more in compressed air; rapier is slower but handles coarse, fancy and many-colour wefts positively.
• Q: Why can a satin fabric be set denser than a plain fabric of the same yarn? A: Satin has far fewer interlacements, so the yarns flatten and move closer before the structure jams.
• Q: What is a starting mark and how is it prevented? A: A weft-density bar formed when the loom restarts after a stop; prevented by fell-position correction, electronic let-off/take-up control and pick-finding before restart.
• Q: How do you select the move number for a 7-end satin? A: It must be coprime with 7 and not 1 or 6 — so 2, 3, 4 or 5; 1 or 6 would produce a twill, not a satin.
• Q: What is weft insertion rate and why is it quoted instead of rpm? A: It is rpm × reed width in m/min, so it compares looms of different widths fairly on actual weft laid per minute.
• Q: An end breaks repeatedly at one place in the loom shed — what do you check? A: Size add-on and film quality, a rough or sharp dent/heald eye, excessive warp tension or shed height, a damaged drop wire, and beam-to-loom alignment.
• Q: What causes a reed mark? A: A bent, choked or wrongly dented reed, or incorrect denting order, giving uneven end spacing visible as a lengthwise streak.
• Q: In which standard atmosphere are Indian fabric tests conditioned? A: The tropical standard atmosphere, 27 ± 2 °C and 65 ± 2 % RH (IS 6359), unlike the 20 °C ISO 139 atmosphere.

Common mistakes

• Calling take-up and let-off "primary" motions, or omitting the warp-protector motion from the auxiliary list.
• Forgetting crimp when converting cloth length to beam length, or cloth width to reed width — the answer is then short by 5–10%.
• Mixing units in production sums: picks/cm with inches, or forgetting the ÷100 that converts cm of cloth to metres.
• Using 590.5/Ne and 1000/Nm interchangeably, or applying the cover-factor formula (which is an English-count formula) to tex values directly.
• Choosing an invalid satin move number (1, repeat − 1, or one sharing a factor with the repeat) and drawing a twill by mistake.
• Assuming higher loom speed increases PPI, or that doubling rpm doubles output when efficiency and stop rate fall at speed.
• Quoting a remembered IS number or GST rate without checking the current edition or notification — many IS numbers have been revised or withdrawn.

Related topics

• Knitting · Nonwovens · Yarn manufacture (spinning) · Weaving preparatory: winding, warping and sizing · Fabric structure and design (dobby and jacquard) · Textile testing and quality control.