Engineer Textile cheat sheet

Fibre classification: natural (cellulosic: cotton, flax, jute; protein: wool, silk) vs man made (regenerated: viscose, lyocell, acetate; synthetic: polyester, nylon, acrylic, polypropylene, elastane).

Cotton fibre: cellulose I, degree of polymerisation ~2000-10000, convoluted ribbon, lumen present; moisture regain 8.5% at 65% RH/20 °C.

Wool: keratin with disulphide cross-links; scales give differential friction (felting); regain ~16%; burns with smell of burnt hair, self-extinguishing.

Polyester (PET): regain ~0.4%, tenacity 4-7 cN/tex, initial modulus high; melts ~250-260 °C and thermoplastic, so heat-setting is possible.

Viscose: regenerated cellulose, tenacity 1.5-2.5 cN/tex dry but only 0.7-1.2 cN/tex wet; low wet modulus causes easy deformation when wet.

Linear density conversions: 1 tex = 1 g/1000 m; 1 dtex = 1 g/10 000 m; Nm (metric count) × tex = 1000; denier = 9 × tex.

Tenacity conversion: cN/tex × density (g/cm³) ÷ 0.981 ≈ g/denier; tenacity in g/den × 0.0883 ≈ cN/tex for approximate work.

Fibre identification sequence: burning test (odour, ash, flame behaviour), then solubility tests, then confirm by IR spectroscopy or microscopy.

Carding: opening, cleaning and individualisation into a sliver; carding efficiency measured by nep count and trash removal %; cylinder-wire settings control fibre damage.

Draw frame: drafting with roller pairs; doubling N slivers improves evenness by √N (random arrangement); autolevelling corrects long-term mass variation.

Comber: removes short fibres below a set length (noil %), raising yarn strength and lustre; typical combing fraction 12-20% noil for fine cotton.

Ring spinning: traveller speed and yarn tension determine end breaks; spindle speed limited by yarn tension; twist TPI = twist multiplier ÷ √(cotton count Ne).

Rotor (open-end) spinning: rotor speeds 100 000-150 000 rpm, production 3-5× ring, but yarn is weaker with wrapper fibres; best for coarse counts.

Twist factor: tex twist factor α = TPM × √tex; twist direction Z (clockwise) or S; plied yarn twist usually opposite to single yarn twist.

Yarn irregularity CV% relates to limit irregularity: index of irregularity I = CV_actual / CV_limit; higher I means poorer fibre control in drafting.

Winding and clearing: electronic yarn clearers remove thick/thin places and foreign matter; splicing gives a joint strength close to parent yarn, knotting lower.

Woven cover factor: warp cover factor = threads per inch ÷ √(cotton count Ne); fabric cover factor combines warp and weft to predict air permeability and stiffness.

Basic weaves: plain (1/1, maximum interlacing, firmest), twill (2/2 or 3/1, diagonal), satin (long floats, lustre, low interlacing); float length controls drape and abrasion resistance.

Loom cycle: shedding, picking, beat-up, let-off, take-up; warp tension must stay constant from full to empty beam via let-off regulation.

Weft insertion rate (picks/min × reed width) determines productivity; shuttleless systems (rapier, projectile, air-jet, water-jet) dominate high-speed weaving.

Weft knitting: single jersey uses one needle bed; stitches per course and wales per inch define stitch density; loop length (mm) is the key control parameter for GSM.

Warp knitting (tricot, raschel) uses a warp sheet and guide bars; run-in ratio per guide bar controls fabric structure and elasticity.

Nonwoven bonding routes: needlepunch (mechanical entanglement), spunlace (hydroentanglement), thermal calendar/air-through, and chemical/binder; each sets different strength and softness.

Nonwoven mass balance: GSM = (fibre mass per area); needlepunch line speed and punch density (punches/cm²) trade off against fabric strength and fibre damage.

Singeing removes protruding fibres (gas flame or contact); desizing removes size (enzymatic for starch, oxidative for PVA) before dyeing to avoid uneven absorbency.

Scouring removes waxes, pectins and oils with alkali plus surfactant; cotton weight loss ~4-8%; mercerising with 18-25% NaOH improves lustre, strength and dye uptake.

Bleaching with hydrogen peroxide (alkaline, 90-98 °C, stabiliser) removes natural colour; residual peroxide must be destroyed (catalase or reducing agent) before reactive dyeing.

Reactive dyeing: exhaustion then fixation in alkali; unfixed dye must be soaped off; fixation % typically 60-80%; salt promotes exhaustion, alkali drives covalent reaction.

Pad-dry-cure for resin finishing: add-on controlled by nip pressure and pick-up %; curing temperature/time sets cross-link density and formaldehyde release.

Dyeing machinery choice: beam/package for yarn and fabric under tension, winch/jet for delicate knits, jigger for open-width woven, continuous pad-steam for bulk.

Liquor ratio (L:R) affects dye concentration and exhaustion kinetics; lower L:R saves water and energy but risks unlevelness in package dyeing.

Effluent parameters: BOD, COD, colour, pH, TDS; reactive dyeing generates high salt load, so low-salt reactive systems and dye recovery are preferred.

Dye-fibre affinity rules: reactive/direct/vat on cellulose; acid/metal-complex on wool, silk and nylon; disperse on polyester, acetate and polypropylene (with carriers or high temperature).

Disperse dyeing of polyester: high-temperature (130 °C) or carrier method; Thermosol (pad-dry-bake 190-210 °C) for continuous; reduction clearing removes surface dye.

Colour measurement: K/S from Kubelka-Munk; colour difference ΔEab combines ΔL, Δa*, Δb*; pass/fail tolerance typically ΔE ≤ 1.0 for critical matching.

Metamerism: two samples match under one illuminant but not another; check with at least D65 and A illuminants and use spectrophotometer curves, not the eye alone.

Shrinkage control: compressive shrinkage (Sanforizing) for cotton woven; heat-setting for synthetics; relaxation drying for knits to reach stable dimensions.

Functional finishes: easy-care (cross-linked cellulose), water repellent (fluorocarbon or wax), flame retardant (phosphorus/nitrogen for cellulose), antimicrobial, softener.

Fastness tests: washing, rubbing (crock), light, perspiration; ratings 1-5 (grey scale); reactive dyes generally good to washing but poor to chlorine bleaching.

Stenter control: temperature zones, overfeed %, pin/clip width; overfeed raises residual shrinkage and GSM, underfeed increases width and reduces elongation.

Sampling and conditioning: standard atmosphere 20 ± 2 °C, 65 ± 4% RH; samples must be preconditioned and equilibrium-tested or results are not comparable.

Yarn strength: single-thread tensile test reports tenacity (cN/tex) and elongation %; lea strength (skein) is used for count-strength product control.

Fabric tensile: strip method (20 mm or 50 mm width) vs grab method; elongation at break and initial modulus differ with method, so report the standard used.

Tearing strength: Elmendorf pendulum method; tear resistance depends on float length and yarn friction; low interlacing (satin) tears easily.

Abrasion and pilling: Martindale rubs to end-point (hole or mass loss) and pilling grade 1-5; pilling is influenced by fibre tenacity, crimp and yarn twist.

Air permeability (mm/s or L/m²/s) is controlled by cover factor, yarn twist and finishing; used for filters, parachutes and sportswear specification.

Colour fastness and dimensional stability: report change in length/width % after specified wash cycles; knit shrinkage limits often ±3% to ±5% depending on end use.

Statistical quality: mean ± 2SD covers ~95% of a normal distribution; Cpk ≥ 1.33 is a common capability target for a controlled textile process.

ISO 9001 is the quality management system standard; ISO 17025 applies to testing and calibration laboratory competence; accreditation is not the same as certification.

AQL sampling (ISO 2859-1): lot size and inspection level set sample size; AQL defines the acceptable percent defective; Ac/Re numbers decide acceptance or rejection.

4-point fabric inspection: assign 1-4 penalty points per defect by length; acceptance commonly ≤ 20-28 points per 100 square yards depending on buyer contract.

ASTM D and ISO test methods must be cited with year; changing method (e.g., strip to grab) changes result values and breaks comparability.

Care label and fibre content rules: many markets require fibre composition percentages and care instructions; Oeko-Tex Standard 100 limits harmful substances by product class.

Colour approval chain: lab dip, bulk sample, production approval; keep a retained standard under controlled storage because dyes and substrates shift over time.

Corrective action loop: nonconformity → root cause (5-why, fishbone) → corrective action → verification; record traceability from fibre lot to finished roll.

Calibration and maintenance records for tensile testers, balances and ovens are mandatory evidence in audits; out-of-calibration data must be quarantined.

Preventive maintenance schedules are set by running hours or production volume; card wire, spindle tapes and loom reed need periodic inspection for wear.

Vibration analysis and thermography detect bearing wear and misalignment before breakdown; condition-based maintenance reduces unplanned stoppages.

Loom automation: electronic let-off/take-up, automatic weft repair, and servo-driven shedding improve pick rate and reduce fabric defects.

Spinning automation: auto-doffing, link winding and electronic clearer data feed mill dashboards; online monitoring of end breaks per 1000 spindle hours is a key KPI.

Drive and control: variable frequency drives on fans and pumps cut energy roughly with the cube of speed for centrifugal loads; inverter harmonics must be filtered.

Lubrication discipline: correct grade and interval for high-speed spindles and loom gearboxes; over-lubrication causes staining and oil spots on fabric.

Machine safety: interlocks on guards, emergency stops, and lockout/tagout before clearing jams; loose clothing near carding and drafting zones is a serious hazard.

Spare-part criticality: classify by lead time and failure impact; long-lead items (card wire, loom cam, servo motor) need buffer stock to protect OEE.

Cost build-up: fibre + yarn + processing + energy + labour + overhead + depreciation + wastage + margin; fibre is usually the largest single cost in a spun yarn.

Wastage allowances: cotton spinning typical invisible loss 2-4%, plus noil and card waste; costing must use net fibre input, not gross purchase weight.

Efficiency and OEE: OEE = availability × performance × quality; a loom shed at 85% efficiency means actual picks are 85% of rated picks.

Capacity planning: machine hours required = (order quantity × standard time per unit) ÷ efficiency; compare with available machine hours per period.

Labour productivity: metres per operator-hour or kg per operator-hour; work study (time and motion) sets standard time and incentive schemes.

Break-even: fixed cost ÷ (selling price − variable cost per unit); contribution margin per machine hour ranks products when capacity is the constraint.

Energy cost per kg or per metre is tracked separately; compressed air and stenter drying are common hidden energy sinks in textile plants.

Lead time = process time + queue time + transport; reducing batch size and setup time (SMED) cuts work-in-progress and improves delivery reliability.

Geotextiles: woven, nonwoven and knitted; key properties are tensile strength, puncture resistance, permittivity and clogging resistance for drainage and separation.

Medical textiles: nonwoven drapes and gowns need barrier (hydrostatic head) plus breathability; implantable grafts need biocompatibility and controlled porosity.

Protective clothing: flame-retardant aramids and modacrylics; thermal protective performance (TPP) and radiant heat resistance determine the protection rating.

Composites: reinforcement in woven, UD or multiaxial form; fibre volume fraction and interface sizing control strength; textile preforms enable near-net-shape.

Filtration: filter media selected by micron rating, air permeability and dust-holding capacity; surface filtration vs depth filtration depends on fibre and bonding.

Smart textiles: conductive yarns, printed sensors and e-textile interconnects; wash durability and strain relief are the main reliability constraints.

Coated and laminated fabrics: adhesion and coating weight per m² determine waterproofing and peel strength; breathable membranes use hydrophilic or microporous films.

Product development loop: define end-use performance spec → select fibre/structure → prototype → test to standard → iterate; cost target checked at each stage.

Water footprint: conventional cotton dyeing can use 100+ L per kg of fabric; low liquor ratio, cold pad-batch and reuse can cut this substantially.

Energy and emissions: stenter and boiler flue gases dominate; heat recovery, insulation and correct air/fuel ratio reduce fuel per kg of fabric.

Effluent treatment: primary (screening, equalisation), secondary (biological, activated sludge) and tertiary (colour removal by ozone, membranes, adsorption).

Chemical management: maintain a restricted substances list (RSL), safety data sheets and ZDHC-style input control; substitute hazardous dyes and carriers.

Sustainability standards: GOTS (organic), GRS (recycled content), RCS, bluesign and Higg Index tools; each has its own scope and verification rules.

Occupational safety: dust control in carding and blowing rooms (respirable dust limits), noise protection in weaving, and solvent vapour control in coating.

Waste hierarchy: reduce, reuse, recycle, recover, dispose; yarn and fabric waste can be shredded for recycled fibre, but fibre length loss reduces quality.

Circularity limits: mechanical recycling shortens fibre and lowers tenacity; chemical recycling (PET to monomer, cellulose to pulp) restores quality at higher cost.

Tensile test speed and gauge length must be fixed and reported; viscoelastic fibres show higher strength at higher strain rates, so results are rate-dependent.

Bursting strength (diaphragm or ball) suits knits and nonwovens better than strip tensile because they stretch in multiple directions.

Stiffness and drape: bending length and flexural rigidity from Shirley stiffness tester; lower rigidity means better drape and softer handle.

Moisture management: wicking rate, vertical wicking height and drying time characterise sportswear comfort; test after the specified number of washes.

Thermal comfort: clo and thermal resistance (tog) measured on guarded hot plate; air permeability and thickness strongly influence insulation.

Colour measurement geometry: 10° observer and D65 illuminant standard for textile pass/fail; specular included vs excluded changes ΔE values, so fix the geometry.

Fastness rating: grey scale for staining and change in colour, 1 (poor) to 5 (excellent); half steps allowed; light fastness uses blue wool standards 1-8.

Test uncertainty: report the method, number of specimens, mean and CV%; a single specimen result is not a valid basis for a specification decision.