What Is Yarn Feeding Tension in Knitting?

Yarn feeding tension, or yarn input tension, is the tensile force acting on yarn as it travels from the package through guides, detectors, tensioning devices, and feeders toward the knitting elements. It is a dynamic process value, commonly expressed in centinewtons or grams-force depending on equipment. It is not the same as stitch length, machine “tension” setting, yarn tensile strength, or fabric take-down. A useful control records where, when, and at what machine speed the force was measured.

Tension accumulates along the complete path from package to needle

The first source is package withdrawal. Package diameter, winding density, traverse pattern, surface condition, cone angle, over-end balloon, unwinding direction, and the presence of knots or splices can change resistance. As a package empties, its withdrawal geometry changes. Two cones from the same yarn lot can therefore deliver different instantaneous forces if package build or path differs.

Each eyelet, tube, guide, detector, brake, and tension disc adds contact. The relationship is not simply additive: friction amplifies tension around changes in direction, while yarn speed and acceleration make the force fluctuate. Lint, damaged ceramics, grooves, contamination, misalignment, and an extra wrap around a guide can turn a stable nominal setting into a different operating condition. The number and angle of contacts must remain part of the threading specification.

Yarn itself changes the path. Linear density, twist, hairiness, fibre friction, finish, moisture content, extensibility, ply construction, and surface geometry all affect withdrawal and yarn-to-metal friction. Waxing or lubrication can improve running by reducing and regularising contact friction, but amount, distribution, chemistry, and ageing matter. A replacement cone with the same count and composition is not necessarily a process-equivalent yarn.

The force is also time-dependent. A carriage reversal on a flat machine, acceleration after a stop, an intermittent jacquard feed, a carrier change, or a high-speed circular machine creates transient peaks that a slow spot reading may miss. Research on flat weft knitting has observed oscillatory tension through the loop-formation cycle, with high values during yarn laying and drawing-down. The relevant control is therefore a working range and variation profile, not a single static number detached from the cycle.

Passive tensioning, storage feed, positive feed, and constant-tension control solve different problems

A passive tensioner creates resistance through discs, springs, gates, or wraps. It establishes a working drag but cannot remove every upstream disturbance. If package withdrawal rises, output tension may rise with it. A storage feeder accumulates yarn on a drum or wheel so package withdrawal is partly decoupled from immediate machine demand. Its storage level, input side, output geometry, and operating limits still require control.

A positive feed system drives yarn delivery at a defined rate or length relative to machine motion. On multi-feed circular knitting, matched driven feeders help equalise the yarn length delivered by the different feeds. Positive delivery reduces dependence on the needles drawing whatever yarn the path permits, but it does not make friction or input tension irrelevant. Poor grip, belt variation, wrap angle, slippage, contaminated wheels, or unstable tension before the feeder can disturb delivery.

Constant-tension feeders use sensing and active control to regulate yarn force while also monitoring speed or consumption. BTSR's equipment documentation, for example, separates programmable tension from absorbed yarn length and yarn-running speed. That distinction is useful: a system may hold a tension target while delivery changes with demand, or control delivery while tension varies within a permitted window. Equipment capability does not remove the need for a product-specific set point.

The correct system depends on machine architecture and yarn. A stable spun-yarn course on a circular machine, an intermittent intarsia carrier on a flat machine, and an elastomeric plated end do not present the same demand pattern. In plating, each component requires an individually controlled path because unequal force and geometry can reverse face/back position or alter elastomeric extension.

Variation can change loops before it becomes a visible defect

Input tension can influence the amount and state of yarn reaching loop formation. Yarn elongates under load and recovers after the loop is formed; friction can also allow a needle to draw yarn back from adjacent loops, a mechanism known as robbing-back. Classic experimental work by Knapton and Munden showed that yarn friction could create substantial loop-length variation at nominally fixed machine settings. This is why cam setting alone cannot prove that the delivered construction is constant.

If average delivery shifts, finished width, course density, wale density, mass per area, hand, opacity, drape, and dimensional response can shift with it. If one feeder or package differs periodically, the result may appear as coursewise barré. If a path varies intermittently, the surface may show isolated tight or slack courses, edge distortion, motif displacement, or inconsistent panel length.

Excessive tension increases yarn extension and the load developed in the knitting zone. Depending on yarn strength, friction, needle action, and structure, it can cause filament splitting, fibre stripping, breakage, press-off, dropped loops, or holes. Transfers, tucks, narrow sections, and high bed occupancy can narrow the process window because yarn must clear or move between elements without excessive resistance.

Very low or unstable tension is not automatically safer. Slack can produce loops around guides, poor detector response, carrier snagging, plating inversion, uneven selvedges, or yarn entering the needle hook from an unintended position. The objective is not the lowest possible force but a controlled force compatible with the yarn, machine, structure, speed, and appearance.

Tension should also be distinguished from the cause of a visual line. A vertical needle line follows a wale and usually points toward a local knitting element or wale-specific condition. Feed-tension variation more often follows time or feed sequence and can create coursewise or repeated bands. Direction, repeat, continuity, and relation to machine positions help isolate the source.

Measure the running path and preserve the conditions around the number

A hand pull is not a tension measurement. Use a calibrated yarn-tension meter or installed sensor suitable for yarn count, speed, and expected force. Place it at a defined point without creating an unrealistic wrap angle. A reading before a feeder describes a different zone from a reading between feeder and knitting point. If both matter, record both rather than treating them as one value.

Dynamic logging is preferable when peaks or periodic variation are suspected. Record average, minimum, maximum, and variation over enough machine cycles to capture carrier reversals, feeder repeats, starts, and speed transitions. Compare positions, packages, and sides under the same speed and threading. A stable reading on a stopped or slowly jogged machine does not establish stability at production speed.

The technical sheet should identify supplier, yarn reference, lot, count, ply, twist, finish or wax, package type, withdrawal direction, thread path, guide and tensioner configuration, feeder type, wheel or belt setting, wraps, sensor position, target and tolerance, machine speed, stitch-length setting and verified loop length, take-down reference, programme version, and atmospheric condition where relevant. Photographs or a threading diagram can prevent small path differences from becoming invisible substitutions.

When a fault appears, change one factor at a time where practical. Exchange packages between positions, inspect contact surfaces, clean and rethread, compare tension traces, verify delivered course length, and examine greige and relaxed fabric. Correcting the symptom by opening the stitch or increasing take-down may move the defect while changing the approved textile. Diagnosis should preserve the relationship between process input and finished result.

Common questions about yarn feeding tension

Feeding tension is a process condition, not a styling correction

When package, path, force, delivery, loop length, and take-down are recorded separately, the factory can reproduce an approved fabric without relying on an ambiguous “tension” instruction. That clarity is particularly important when several yarns, feeders, carriers, or stitch groups form one garment.

Examples of material and construction development appear in Work. The Process page sets out the relationship between stitch development, sampling, fitting, and factory handoff. Further context is available in About, and development enquiries can be submitted through the contact form.