UPMSP Weaving Technology cheat sheet

Cotton fibre: cellulose polymer, moisture regain ~8.5% at 65% RH, tenacity 3–5 g/den dry; strength increases ~10–20% when wet.

Wool: protein (keratin), regain ~16%, elastic recovery high; scales give felting shrinkage and directional friction effect (D.F.E.).

Silk: continuous filament, triangular cross-section, ~20% of fibre weight lost as sericin in degumming; tenacity 3.5–4.5 g/den.

Regenerated cellulose (viscose): regain ~13%, wet tenacity drops to 40–50% of dry - a key reason for gentle warp tension sizing.

Synthetic fibres: polyester regain ~0.4%, nylon ~4.5%, acrylic ~2%; low regain means static generation and need for antistatic sizing.

Yarn count systems: Tex = g/1000 m; English cotton count Ne = 840 yd/lb, so Tex × Ne ≈ 590.5.

Twist multiplier TM = TPI / √Ne; higher TM gives harder, livelier yarn with lower elongation at break.

Ply yarn resultant count: Ne(ply) = Ne(single)/n for same-count plies; strength is less than n × single due to twist interaction.

Plain weave: repeat 2×2, maximum interlacement, highest crimp and cover factor; basis for poplin, cambric, voile.

Twill weave: repeat 3 or more; 2/1 and 3/1 Z-twill common. Float length = weave step; longer floats give softer hand and higher lustre.

Satin/sateen: repeat ≥5, float length n−1; warp-faced satin uses step 2 or 3 with n≥5; sateen is weft-faced.

Crimp % = ((yarn length in fabric − fabric length)/fabric length) × 100; warp crimp usually exceeds weft crimp in plain weave.

Cover factor K = (threads per inch)/√Ne; fabric cover factor = K_warp + K_weft − (K_warp × K_weft)/28 for cotton.

Weave repeat drafting: number of heald shafts needed ≥ longest float + 1 for clean selvedge on simple weaves.

Derivative weaves: warp rib (thick/thin picks), weft rib, matt/panama (grouped ends and picks), and herringbone (reversed twill).

Balanced fabric: warp and weft count and sett similar; unbalanced fabric shows higher crimp in the finer/lower-sett direction.

Primary motions: shedding, picking, beat-up. Secondary: let-off and take-up. Tertiary: warp stop, weft stop, selvedge, temple.

Crank shedding suits plain weave only; dobby handles small repeats (up to ~32 shafts); jacquard handles unlimited design size.

Picking timing: shuttle must clear the shed before shed crossing; early shedding causes trapping and broken ends.

Beating-up occurs at shed crossing (front centre); sley eccentricity determines dwell and beat-up force.

Let-off tension control: negative let-off uses weights/levers; positive let-off is gear or motor driven for constant warp tension.

Take-up: 5-wheel or 7-wheel pick wheel sets picks per inch; change gear ratio determines picks/inch = constant/gear teeth.

Warp stop motion uses drop wires; electrical contact type stops loom within one pick on broken end.

Loom speed vs picks per inch: production (m/min) = (RPM × 60)/(PPI × 39.37).

Warping types: direct/beam warping for long runs; sectional warping for short runs, stripe patterns and coloured warps.

Sizing add-on % = ((sized yarn weight − unsized weight)/unsized weight) × 100; cotton warp typically 6–12% add-on.

Size recipe components: adhesive (starch/PVA), lubricant, binder, and preservative; PVA gives better film but higher BOD in effluent.

Size box temperature and viscosity control: starch size cooked at ~95–98 °C; viscosity measured by funnel (TVA) or rotoviscometer.

Squeeze roller pressure controls wet pick-up; higher pressure lowers add-on and improves drying economy.

Drying: cylinder drying is most common; size migration to surface causes hairiness and shedding at drop wires.

Warp breakage during sizing is reduced by lease rods, proper thread separation and correct tension zone control.

Slasher production (kg/h) = (ends × yarn tex × speed m/min × 60 × efficiency)/(1000 × 1000).

Loom efficiency % = (actual picks delivered/calculated picks at running time) × 100; typical shed efficiency 85–95%.

Production per loom per shift = (RPM × 60 × minutes × efficiency)/(PPI × 39.37).

Stoppage classification: warp breaks, weft breaks, mechanical, and knotting/tying; Pareto analysis targets the largest cause first.

Weaver allocation (loom load) = available time per shift / (stoppage time per loom + attendance time per loom).

Warp break rate per 100,000 ends per hour = (breaks × 100,000)/(ends × hours).

Weft break rate is expressed per 100,000 picks; high rates point to pirn quality, shuttle tension or air pressure.

Work study: time study gives standard time; allowance typically 10–20% for personal, fatigue and delay.

Knotting and gaiting time is non-productive; warp tie-in reduces gaiting time by up to 70% versus re-drawing.

Warp way defects run along warp: missing end, broken end mark, tight/loose end, wrong drawing, end out.

Weft way defects run across: missing pick, double pick, thick/thin place, weft crack, shuttle mark, starting mark.

Reed marks arise from incorrect denting or damaged reed wire; appear as regular warp-way streaks.

Cockle and slub are yarn faults; knots and slubs must be removed by clearer or splicer before weaving.

Holes and cut selvedge indicate temple, reed or shuttle damage; temple marks come from worn temple rings.

Stains and oil marks come from loom lubrication, dirty fluff or wet sizing; often rejected in greige inspection.

Fabric shrinkage and bowing/skewing after wet processing trace back to twist liveliness and weft insertion tension.

Defect points systems (e.g., 4-point) assign 1/2/3/4 points by defect length; total points per 100 sq yd drives grade.

Inspection machines: perching (visual), 4-point grading, and fabric scanning with cut-length control.

4-point system: defect ≤3 in = 1 point; >3–6 in = 2; >6–9 in = 3; >9 in = 4 points; holes ≤1 in = 2 points regardless.

Acceptance limit commonly 20 points per 100 sq yd; a roll with more is downgraded.

Sampling plans per ISO 2859-1 use AQL levels; AQL 2.5 is typical for apparel greige fabric.

Tests on greige: ends/picks per inch (counting glass), crimp, weight per sq yd, width, tensile and tear strength.

Colour fastness and shade variation assessed by spectrophotometer or grey scale; lot-to-lot variation is a key customer complaint.

Standard test atmosphere: 20 ± 2 °C and 65 ± 2% RH; samples conditioned 24 h before testing.

Quality cost includes prevention, appraisal, internal failure and external failure; internal failure is cheaper than external.

Fabric weight (g/m²) = (warp tex × ends/m + weft tex × picks/m)/1000, adjusted for crimp.

Fabric weight (oz/yd²) = g/m² × 0.0295; reverse: g/m² = oz/yd² × 33.906.

Yarn requirement (kg) = (fabric length × width × g/m²)/1000, then divide by (1 + crimp) for warp and weft separately.

Cost per metre = (warp yarn cost + weft yarn cost + sizing + weaving + processing + overhead + profit)/metres produced.

Yarn cost = weight (kg) × rate per kg; add sizing add-on % to warp weight before costing.

Loom-hour cost = (depreciation + power + labour + maintenance)/loom hours available; drives conversion charge per metre.

Break-even production = fixed cost / (selling price per metre − variable cost per metre).

Power cost per metre = (motor kW × hours × unit rate)/metres produced; loom motor load typically 1–3 kW.

Preventive maintenance schedule: daily (lubrication, fluff cleaning), weekly (reed, heald, sley check), monthly (gear, bearing, clutch).

Loom lubrication: over-oiling causes stains; under-oiling causes wear and pick faults - follow OEM interval and quantity.

Lockout/tagout before clearing jams; loom must be at rest and clutch disengaged.

Guards required: picking stick, sley, gear covers, and interlocked gates on shuttle looms.

Noise exposure limit 90 dB(A) for 8 h; shuttle looms often exceed 100 dB(A), requiring hearing protection.

Fire safety: cotton dust is combustible; dust extraction and no smoking in the weaving shed.

Workshop tools: reed hook, heald hook, pick glass, feeler gauge, and torque wrench for setting sley and reed.

Accident reporting and near-miss logging feed the safety committee; PPE includes ear plugs, goggles and aprons.

Weft insertion rates: projectile ~1,000 m/min, rapier ~1,200 m/min, air-jet up to 2,500 m/min, water-jet ~2,000 m/min.

Air-jet: main nozzle plus relay nozzles; requires profiled reed and controlled air pressure/timing; best for spun and filament staple.

Water-jet: high speed, low noise, suited to synthetic filament; needs drying after weaving.

Rapier: flexible or rigid; handles wide range of yarns including glass and heavy denim; lower speed than air-jet.

Electronic let-off and take-up with servo motors give constant tension and quick style change.

Automation: electronic dobby/jacquard, automatic pick finding, on-loom monitoring (OEE), and automatic weft repair.

Quick style change (QSC) reduces gaiting time; auto-doffing and warp tie-in raise loom utilisation.

Energy monitoring per loom and predictive maintenance using vibration/temperature sensors are current trends.