UPMSP Weaving Technology key terms

The set of parallel, lengthwise yarns held under tension on the loom. They run vertically through the fabric and must be strong and well prepared because they endure repeated shedding and beat-up.

The yarn inserted crosswise between the warp threads during weaving. It forms the horizontal elements of the cloth and is usually less tightly twisted, softer, and lower in strength than warp yarn.

A number expressing yarn thickness or linear density. Direct systems (tex, denier) give mass per fixed length; indirect systems (Ne, cotton count) give length per fixed mass. Higher indirect count means finer yarn.

A direct yarn numbering system defined as grams per 1000 metres of yarn. It rises as yarn gets thicker. A 20 tex yarn has 20 g per km, and the SI unit decitex equals one-tenth of a tex.

A measure of how much twist a yarn carries relative to its thickness, calculated as turns per unit length divided by the square root of the indirect count. It allows twist levels of different yarn counts to be compared fairly.

A calculated value showing how completely warp and weft yarns cover the cloth surface, derived from yarn count and thread spacing. Higher values mean denser, less porous fabric with reduced air and light transmission.

The number of warp threads contained in one inch of fabric width, abbreviated EPI. It is counted in a reed or from a fabric sample and directly controls warp density, cover, and the reed plan used on the loom.

The number of weft threads contained in one inch of fabric length, abbreviated PPI. It reflects the beating rate relative to cloth take-up and determines weft density, fabric weight, and firmness of handle.

The simplest interlacing in which each warp end passes alternately over and under successive weft picks. It gives maximum firmness and interlacing, needs many heald frames, and produces fabrics such as sheeting and poplin.

A weave producing diagonal lines on the fabric surface, made by advancing the interlacing point one end and one pick per step. Twills are softer and drape better than plain weave and allow longer floats.

A weave in which interlacing points are distributed so that no two touch, giving long floats and a smooth lustrous face. Warp-faced satin shows mostly warp; weft-faced sateen shows mostly weft.

A portion of a warp or weft yarn that passes over two or more yarns of the opposite direction without interlacing. Long floats give lustre and looseness but reduce abrasion resistance and snag resistance.

The smallest number of ends and picks after which the interlacing pattern repeats in both directions. It determines the minimum heald frame requirement, the peg or dobby plan, and the design paper area used.

A diagram showing which warp ends are threaded on which heald frames and in what order. It links the weave design to the loom harness and must be consistent with the lifting plan for correct interlacing.

A grid showing which heald frames are raised at each pick to produce the required weave. It is programmed into the dobby or jacquard and is read together with the drafting plan.

The primary loom motion that divides the warp into two layers to form a triangular opening called the shed, through which the weft is inserted. It may be crank, cam, dobby, or jacquard type.

The opening formed in the warp when some ends are raised and others lowered during shedding. Its shape and timing affect yarn strain, weft insertion clearance, and the quality of the woven selvedge.

The loom motion that inserts a weft pick across the shed, using a shuttle, projectile, rapier, air jet, or water jet. It is a secondary motion and its timing must match shed opening and beat-up.

The motion in which the reed pushes the newly inserted pick to the fell of the cloth, setting weft spacing. Beat-up timing and force influence pick density, fabric firmness, and the risk of warp end breakage.

A secondary loom motion that winds finished fabric onto the cloth roller at a controlled rate, setting picks per inch. It works together with let-off to maintain consistent warp tension and pick density.

A secondary loom motion that releases warp from the beam as weaving proceeds, keeping warp tension steady as the beam diameter decreases. It may be negative or positive and directly affects fabric quality.

The longitudinal force on the warp yarns during weaving, usually expressed in newtons per end. Too little tension causes loose ends and poor shed clarity; too much causes end breaks and fabric width loss.

The sequence of operations converting warp yarn into a loom-ready beam: winding, warping or creeling, sizing, and drawing-in or tying-in. Good preparation reduces breakage and defects during weaving.

Applying a starch or synthetic film to warp yarns to increase strength, reduce hairiness, and improve abrasion resistance during weaving. Size add-on, penetration, and evenness are controlled and later removed in finishing.

The percentage of size material by weight left on the sized warp relative to the unsized yarn weight. It must be high enough to protect yarns but low enough to avoid shedding problems and high desizing cost.

Equipment that passes warp sheets through size liquor, then dries and winds them onto a loom beam under controlled tension. Key settings include squeeze pressure, drying temperature, stretch, and winding tension.

Threading each warp end through a drop wire, a heald eye, and a reed dent according to the drafting plan. It is done manually or by machine and must match the weave design exactly.

A comb-like part with fine wire dents that spaces warp ends and beats each pick to the fell. Reed count is expressed in dents per inch or per two inches and determines ends per inch with the drawing-in plan.

A frame carrying heald wires with central eyes through which warp ends are threaded. Frames are raised and lowered by the shedding mechanism to form the shed according to the lifting plan.

A shedding mechanism controlling a moderate number of heald frames, typically up to 24 or 32, for small repeating weave designs. It is programmed by pegs, chains, or electronic actuators.

A shedding system in which each warp end can be controlled individually, allowing large and complex designs such as figured fabrics. Capacity is stated by the number of hooks or cords.

The speed at which weft is inserted, often expressed in metres per minute. It is a fairer comparison of loom productivity than picks per minute because it accounts for fabric width.

Actual picks woven expressed as a percentage of the theoretical picks possible in the same running time. Stops for warp breaks, weft breaks, and knotting reduce efficiency and are recorded on the loom counter.

Failure of a warp end during weaving, usually from abrasion, weak yarn, or excessive tension. Each stop lowers efficiency and creates a mend mark or stop mark if the loom is not restarted correctly.

A visible transverse line or band in the fabric caused by loom stoppage and restart, changing pick spacing at that point. Correct restarting technique and tension control minimise its severity.

The system of classifying and scoring woven fabric faults, such as by points per unit length, to decide acceptance or rejection. Grading rules vary by buyer and standard, so the contract must be checked.

A widely used fabric inspection method in which defects are penalised one to four points according to length, and acceptance is based on points per hundred square yards. It requires a defined inspection speed and lighting.

The line where the latest pick has been beaten against the woven fabric, marking the boundary between cloth and warp sheet. Its position and movement affect pick density and fabric appearance.