Publish Time: 2026-10-12 Origin: Site
A circular knitting machine turns yarn into fabric continuously around a rotating cylinder, at a speed that leaves an operator little time to react. One unplanned stop can cost several hundred kilograms of production, and defects found only after dyeing and finishing cost more than the downtime itself. Few failures begin as failures. They begin as a small shift in tension, a needle that no longer opens cleanly, or a feeder sitting out of position.
Most circular knitting machine problems fall into six families: needle and needle bed faults, dropped and missing stitches, yarn breakage and tension faults, fabric defects, mechanical and drive faults, and lubrication or electrical faults. Nearly all of them give an early warning, and the great majority are corrected through systematic inspection, correct settings and scheduled maintenance rather than replacement of major components.
This guide explains how each family behaves and sets out the troubleshooting order and maintenance routine that keep a machine producing.
The faults reported most often are needle breakage and wear, dropped and missing stitches, yarn breakage from incorrect tension, fabric holes and vertical lines, uneven stitch density, vibration, and stops caused by lubrication, lint or sensor problems. Needle and yarn faults cause most unplanned downtime, while fabric defects cause most quality losses.
A circular knitting machine knits by coordinating five systems: the needles and needle bed, the cams and sinkers, the yarn feeding, take-down, and drive and control systems. A fault in any one shows up in the fabric first, because the fabric records every stitch the machine has made.
Fault Family | Typical Symptoms | First Component to Check |
Needle and needle bed | Broken needles, holes, vertical lines, defects repeating at one position | Needle condition, needle groove, cam track |
Dropped and missing stitches | Holes, ladders down the fabric, gaps in the pattern | Needle latch, sinkers, needle selection |
Yarn feeding and tension | Uneven density, yarn breakage, loose loops, weight drift | Yarn path, tension device, feed belt |
Fabric defects | Barre, spirality, oil marks, weight or width off target | Stitch cams, yarn lots, take-down |
Mechanical and control | Vibration, overheating, false stops, lint build-up | Belt tension, oil setting, sensors |
Four classes behave differently on the floor. Mechanical and wear faults develop slowly and repeat in the same position. Yarn and feeding faults affect every stitch, so they show across the whole fabric width. Control, sensor and lubrication faults are intermittent. The international standard for knitting machine vocabulary and classification separates machines by needle arrangement, which distinguishes a circular machine from a flat machine.
Needles are the most heavily loaded parts in the machine and the first to wear. A worn, bent or broken needle cannot hold the loop cleanly, so it produces dropped stitches, holes and vertical lines, and a break can damage the cylinder groove and the neighbouring needles. Repeated breakage in the same position always indicates a mechanical cause.
Needles run at high speed against the groove, are driven by the cams on every revolution, and absorb the friction of yarn passing through the hook. The loop-forming cycle that knitting needles perform explains why: the needle clears the old loop, receives new yarn, then casts off, and the latch must open and close at exactly the right moment.
Breakage Pattern | Most Likely Cause |
Random, across the whole cylinder | Insufficient lubrication, wrong oil, or a poor needle batch |
The same position, repeatedly | Damaged groove, worn cam, or a bent needle still in the bed |
Concentrated on one side | Uneven levelling or worn sinkers in that section |
Many needles at once | Foreign object or lint in the knitting zone |
Latch and hook faults are the most common needle failures. A latch that sticks or fails to return will not hold the loop even when the needle body is sound, and a burr or flattened hook grips the yarn and causes breakage. Groove damage is worse, because the cylinder and dial locate every needle and a single damaged groove keeps destroying new needles, so a knitting machine cylinder with widespread wear or a bent body needs professional attention.
A dropped stitch occurs when a needle fails to hold a loop it has already formed, while a missing stitch occurs when a needle is not selected or not moved at all. Dropped stitches repeat in the same position and create ladders down the fabric. Missing stitches are selection or control faults, so they follow the pattern.
A machine that keeps dropping stitches usually has a latch that will not close, yarn not laid properly into the hook, a worn sinker, or take-down tension too low to hold the loop.
Stop the machine safely and mark the position of the defect.
Inspect the needle and its latch, replacing anything that does not move freely.
Check the sinkers in that section.
Trace the yarn path from the package to the feeder.
Verify yarn tension and stitch length, then run a short test knit.
A dropped stitch on a single jersey circular knitting machine is often traced to a single component, because one set of needles gives the fabric little tolerance.
A machine that keeps missing stitches is failing to select the correct needles, so the cause lies in the selection system, the pattern program, or the signal that drives the selectors, not in needle and yarn contact.
Selectors and selector jacks must move freely in their slots, because a sticking selector or a cam out of adjustment leaves a needle in the wrong track. A missing stitch that follows the design is a control or selection problem, while one that ignores the design is mechanical.
Yarn breakage and tension faults are the leading cause of uneven density, weight variation and production stops. They originate in misadjusted tension devices, grooved guides, lint in the yarn path, poor package unwinding, or yarn that does not suit the machine gauge and running speed.
Tension touches every stitch, so a small deviation affects the whole roll. High tension stretches the yarn and accelerates needle wear, while low tension prevents a stable loop from forming and leaves loose, irregular stitches.
The feeder must deliver yarn at a constant rate and stop the machine when yarn does not arrive. Guides are progressively grooved by yarn movement, so they should be treated as wear parts. A yarn tensioner that no longer holds a consistent setting, or a stop motion sensor that is dirty and over-sensitive, generates stops that look spontaneous.
Fabric defects are the visible result of faults elsewhere in the machine, so they are best treated as evidence. Holes usually come from needle or yarn faults, vertical lines from one damaged needle or feeder, uneven density from unequal tension between feeders, and colour bands from mixed yarn lots on the creel.
Defect | Likely Causes |
Holes | Weak or thin yarn, tension too high, damaged latch, stitch too tight |
Vertical lines | Worn or bent needle, one uneven feeder, one faulty knitting section |
Uneven density | Stitch cams set differently between feeders, feed belt slip, needle wear |
Barre | Mixed yarn lots, uneven feed tension between feeders |
Spirality and oil stains | Lively high-twist yarn, too many feeders on single jersey, over-lubrication, a leak |
A double jersey circular knitting machine adds a second set of needles in the dial, so defects can originate in either set.
Spirality appears as wales that lean rather than run straight, and garments cut from the fabric twist after the first wash. The cause is usually yarn twist combined with the geometry of the knitting action, so use yarn with a suitable twist level and agree a finishing route that compensates. Barre is different: horizontal bands of slightly different shade caused by mixing yarn lots on the creel or by uneven feed tension between feeders, and because it becomes obvious only after dyeing it is controlled through yarn lot discipline. Reviewing the terminology and behaviour of knitting elements such as sinkers and cams is worthwhile, because misnamed components lead to adjustments on the wrong part.
Vibration and overheating tell the operator that something is loose, misaligned, under-lubricated or overloaded, and both should be treated as stop signals, because continued running converts a small adjustment into bearing, shaft or cam damage.
Belt tension is easy to leave unchecked. A loose belt slips, producing uneven fabric and rapid belt wear, while an over-tight belt loads the motor bearings, the main shaft and the pulleys. Check tension with a gauge rather than by feel, and confirm pulley alignment. An unlevel machine loads one side of the cylinder more heavily and concentrates defects on one side of the fabric.
Lubrication fails in three ways, as too little oil, too much oil, or the wrong oil. Insufficient lubrication raises friction and heat; over-lubrication creates oil stains in the fabric and attracts lint; and the wrong oil attacks seals and accumulates in the knitting zone. A blocked oil line starves some points while flooding others, so each oil point should be verified as receiving oil. Lint is the other half of the problem, because fibre accumulates around feeders and needles and interferes with the loop cycle when the blowers are not working, so components that collect lint such as the brush carrier should be inspected on the same schedule.
Electrical and sensor faults cause a disproportionate share of sudden stops because they are intermittent. A textile hall combines lint, humidity and vibration, and a dusty sensor, a loose connector or a corroded contact will work correctly most of the time and then produce a false signal at the worst moment.
The usual culprits are the yarn break stop motion, which halts the machine when the tension arm rises because yarn has broken or a package has run out, the needle detector, the lint blower and the feeder solenoids. A dirty stop motion sensor halts the machine while the yarn is intact, and operators learn to restart without investigating, which is the real risk, because the same sensor will eventually miss a genuine fault.
A structured sequence is far more effective than random adjustment. Stop the machine, identify where the fault appears, read the alarm, check components in order from the defect outward, change one setting at a time, and run a short test knit before returning to full production.
Stop the machine safely and record the position of the defect on the roll.
Read the alarm message and check the location it names.
Inspect the fabric and note whether the defect repeats in the same position.
Check the needle, its latch and the related cam area.
Trace the yarn path from the package through the guides to the feeder.
Verify yarn tension and compare every feeder against the others.
Review stitch length, speed and take-down settings, then produce a short test knit.
Record the fault, the cause and the correction before restarting production.
Most recurring problems are documented before they are solved, so recording the machine, yarn lot, defect position and correction turns individual repairs into a pattern that can be corrected rather than patched.
Preventive maintenance is the most cost effective way to reduce circular knitting machine faults, because it addresses worn components, contaminated sensors and lubrication problems before they cause a stop.
Interval | Maintenance Tasks |
Daily | Inspect needles and the knitting zone, check oil level and flow, clean the work area, verify stop motions before production |
Weekly | Clean the needle bed, cylinder and cam area, check belt tension, inspect guides and tension devices, clean sensors and blowers |
Monthly and annually | Inspect sinkers, cams and selector components, verify stitch settings across all feeders, check levelling and bolts, and arrange professional inspection of the cylinder, dial and drive train with replacement of consumable components |
Keeping a stock of commonly replaced circular knitting machine spare parts is part of the same programme, because a machine waiting for a needle set is losing production for a predictable reason.
Repair is usually the right decision when the fault is limited to replaceable components and the machine is otherwise sound. Replacement or escalation becomes the better choice when faults repeatedly disrupt production, when the same failure returns after a correct repair, or when maintenance cost approaches the value of the machine.
Factor | Repair the Existing Machine | Replace or Upgrade |
Immediate cost | Lower, limited to parts and labour | Higher initial investment |
Long-term reliability | Declines as components age | Restored by new components |
Call technical support when needles keep breaking after the groove and cam have been checked, when unusual noise or vibration continues after belts and fasteners have been checked, or when the same alarm returns repeatedly.
Where the same fault returns across several machines or several articles, the machine is usually not the cause. Running a yarn outside the practical window for the gauge, or operating above the speed the fabric structure allows, produces faults no adjustment can remove. Machine specification therefore matters before purchase, because gauge, diameter, feeder count and the yarns available set the practical boundaries of reliable production. No single machine suits every mill, but the machine matched to a defined product range and a realistic maintenance capability will have the lowest long-term fault rate.
Can a circular knitting machine run at full speed immediately after a yarn lot change?
No. Introduce a new lot at reduced speed and inspect the first roll closely, because twist level, count variation and fibre shedding differ between lots and change loop behaviour. Confirming stitch length and feed tension on the first roll prevents a whole batch from carrying a defect that only appears after finishing.
How quickly does a contaminated sensor become a production problem?
It usually causes false alarms long before it causes a missed detection. A dust-covered sensor halts the machine while the yarn is intact, operators learn to restart without investigating, and that habit is the real risk, because the same sensor will eventually miss a genuine fault.
Is it cheaper to replace worn needles individually or as a set?
Individually, in terms of immediate cost, but not in terms of fabric quality. Needles of different age form loops of slightly different size, so mixing new needles with worn ones introduces a density variation that becomes visible after dyeing. Where a section shows general wear, replacing the full set restores uniform loop formation.
WELLKNIT was founded in Taiwan since 1987, and in 1995, we set up the production base in Quanzhou, Fujian, is the first Taiwan-funded weft knitting machine manufacturer to take root in Quanzhou.