In the knitting industry, the knitting machine needle is a fundamental tool that plays a decisive role in the final quality of the product. Whether it’s a high-speed circular knitting machine or a specialized flat knitting machine, the precision and perfect condition of each needle directly influence the fabric’s structure, uniformity, and aesthetic appeal.
Any minor defect on the needle shank, hook, or latch can cause serious faults in the fabric, leading to reduced quality, increased waste costs, and production disruption.
This article will delve into the core function of the knitting machine needle and provide a detailed analysis of the 5 most common fabric faults that originate from the needle, including fabric tears, wrinkles, and stripes.
1. The Core Role of the Knitting Machine Needle
The knitting machine needle is the component that executes the complex knitting cycle (loop creation, yarn drawing, cast-off) through reciprocating motion within the cam track. Despite its simple structure, each needle must ensure 3 main functions:
- Catching and Drawing New Yarn: The needle hook must catch the newly supplied yarn smoothly.
- Securing the Old Loop: The latch must close in time to secure the old stitch loop as the hook moves through.
- Casting Off the Old Loop: The hook must release the old stitch loop cleanly so that the new yarn can form a new loop.
The precision and surface condition of the knitting machine needle are prerequisite factors for this cycle to occur perfectly at high speed.
2. Common Fault 1: Holes and Tears – Direct Physical Damage
Tears or holes are the most severe faults, often requiring the machine to be stopped immediately for resolution. Tears usually appear as single punctures or long rips along the stitch column.
2.1. Fault Mechanism Originating from the Needle
The main cause is that the knitting machine needle has transitioned from a knitting state to a destructive state:
- Broken Hook: When the needle hook breaks, the remaining needle tip forms a sharp, pointed edge. Instead of catching the yarn, this sharp edge snags the previously formed yarns or loops on the fabric, stretching and tearing them. This fault typically appears as a clear puncture hole.
- Technical Solution: The broken knitting machine needle must be replaced immediately. A careful check of adjacent needles and the sinker is necessary to ensure they are not broken or chipped due to collision with the damaged needle.
- Deformed or Stuck Latch: The knitting machine needle latch must open and close under inertial force. If the latch is bent, warped, or stuck partially open by oil residue, it creates a sharp gap. As the needle moves down, this gap scratches and rips the old stitch loop.
- Technical Solution: Intensify cleaning of the needle slots and latches. Only use high-quality knitting oil (typically ISO VG 22 or 32) with self-cleaning capabilities to ensure the needle latch moves smoothly.
2.2. Detection and Prevention Methods
- Needle Inspection: Use a magnifying glass to check the integrity of the needle hook and latch. Small cracks on the hook are early signs of fatigue breakage.
- Rust Prevention: Rust creates rough patches and sharp edges. Store spare knitting machine needle components in a dry, temperature and humidity-controlled environment. When the machine is stopped for an extended period, specialized anti-rust oil must be applied to the entire needle area.
3. Common Fault 2: Vertical Fabric Stripes (Needle Lines) – The Problem of Stitch Uniformity
Vertical fabric stripes are lines running parallel to the stitch column, causing differences in density and light reflection, reducing the aesthetic quality of the fabric. The core cause is the non-uniformity of the Stitch Length.
3.1. Fault Mechanism Originating from the Needle
- Uneven Needle Wear: This is the leading cause. Over time, the knitting machine needle hook wears down, reducing the actual distance between the hook and the knitting point. A worn needle creates a tighter and shorter loop than a new needle. This difference in stitch length (even if only 0.01mm) will create fabric stripes.
- Technical Solution: Implement a Proactive Replacement strategy by replacing all needles simultaneously according to an operating hour schedule (typically 2500–3000 hours) rather than waiting for the needle to break. This ensures all knitting machine needle parts on the cylinder have the same level of wear, maintaining stitch uniformity.
- Butt Height Error: The needle butt is the part that contacts the cam. If the needle butt is bent, worn, or has a manufacturing error, it alters the timing of when the needle is activated by the cam. A needle activated at the wrong time will draw the new yarn from an incorrect position, leading to stitch length deviation.
- Technical Solution: When installing new knitting machine needle components, use needles with extremely low butt height tolerance (below ± 5 microns). Absolutely discard any bent or warped needles.
3.2. Control and Analysis
- Stitch Length Measurement: Use a Stitch Length Meter to determine the difference between stitch columns.
- QC Report Analysis: Only use knitting machine needle components that come with a QC report guaranteeing absolute uniformity in shank thickness and butt height tolerance.
4. Common Fault 3: Fabric Wrinkles and Loop Distortion – Failure Due to Friction
Fabric wrinkles, also known as tight or twisted loops, occur when the knitting machine needle does not move smoothly or when the yarn is excessively pulled due to high friction.
4.1. Fault Mechanism Originating from the Needle
- Bent or Misaligned Needle: The knitting machine needle is slightly bent due to impact or cyclic stress. A bent needle significantly increases friction between the needle shank and the cylinder slot wall. The increased friction causes the needle to move unevenly, leading to a delay in the cast-off process and loop distortion.
- Technical Solution: Use knitting machine needle components with high Core Toughness, vacuum-hardened to increase resistance to deformation. Check the straightness of the needle before installation.
- Damaged Anti-Friction Coating or Rough Needle: Conventional Chrome plating can wear out quickly, exposing the high-roughness steel substrate. When yarn passes through a rough needle, friction increases sharply, causing the yarn to be “pulled” and “twisted” instead of “sliding,” leading to loop tightening.
- Technical Solution: Switch to knitting machine needle components with a DLC (Diamond-Like Carbon) coating. The DLC coating has an extremely Low Coefficient of Friction, allowing the yarn to glide easily over the needle, reducing loop tightening, and enabling the machine to operate at higher speeds without excessive heat generation.
4.2. Lubrication Management
This fault can also be a sign of insufficient knitting oil supply or deteriorated oil. Ensure the knitting oil is of the appropriate viscosity and high anti-oxidation quality to always maintain a perfect lubricating film between the knitting machine needle and the cylinder slot.
5. Common Fault 4: Frequent Yarn Breaks – Cutting Fault
Frequent yarn breaks not only affect productivity (constant machine stops) but also increase stress on the needle, leading to the risk of needle breakage.
5.1. Fault Mechanism Originating from the Needle
The main cause is the presence of sharp edges or gaps in the hook and latch area of the knitting machine needle, transforming the needle from a “knitting device” into a “cutting device”:
- Overly Sharp Hook Edge or Burrs: Although the knitting machine needle hook needs to be sharp to easily catch the yarn, an overly sharp hook edge or burrs due to manufacturing errors/localized wear will cut thin yarns, especially synthetic yarns with low tensile strength.
- Technical Solution: Only use knitting machine needle components from suppliers with strict Hook Profile inspection procedures. Inspect the needle with a microscope before installation to check for burrs.
- Sharp Gap Between Hook and Latch: If the knitting machine needle latch is bent or warped, it can create a small, sharp gap at the contact point with the needle hook. When the yarn passes through or gets caught in this gap under tension, it will be cut.
- Technical Solution: Replace the knitting machine needle immediately upon detecting a bent or incompletely closing latch.
5.2. Cumulative Impact
Yarn breakage also increases when the yarn has poor strength, is defective (knots, fuzz), or when the humidity in the workshop is too low (making the yarn dry and brittle). High-quality knitting machine needle components minimize physical impact on the yarn, compensating for environmental factors or imperfect yarn.
6. Common Fault 5: Dirty Fabric – Surface Hygiene Fault
Dirty or stained fabric with yellow/black streaks is the result of accumulated sludge and oxidized oil, which the knitting machine needle transfers directly onto the fabric.
6.1. Fault Mechanism Originating from the Needle
- High Surface Roughness: Poor-quality or excessively worn knitting machine needle components have high surface roughness (Ra). The rough surface creates micro-holes and grooves where oxidized oil residue, lint, and other dirt particles easily adhere and accumulate.
- Technical Solution: Only use knitting machine needle components that have been professionally surface-treated, achieving extremely high smoothness (typically below Ra 0.2 µm). The use of DLC-coated needles also helps prevent this adhesion.
- Needle Reaction with Lubricating Oil: Needles with incompatible material or surface coating can react with the detergent additives or anti-oxidants in the knitting oil, leading to the formation of chemical sludge.
- Technical Solution: Check the compatibility between the knitting oil brand and the needle manufacturer’s recommendations. Only use specialized, washable knitting oil that has been tested.
6.2. Preventive Cleaning
Regularly clean the needle, sinker, and cylinder area with compressed air or specialized cleaning solution to remove sludge before it has a chance to transfer to the fabric.
7. New Needle Selection Strategy: 3 Mandatory Technical Factors
To prevent the above faults, selecting high-quality knitting machine needle components is the most cost-effective investment strategy. Here are 3 mandatory technical factors to check:
7.1. Absolute Geometric Precision and Micro Tolerance
The difference between a knitting machine needle that causes fabric stripes and a perfect needle lies in tolerance:
- Shank Tolerance: The shank thickness must be absolutely uniform across the entire batch, usually allowing a deviation of only ± 0.005 mm (5 microns).
- Butt Height: The height must be strictly controlled to ensure synchronous activation by the cam, eliminating the risk of vertical stripe faults due to timing deviation.
Reputable knitting machine needle suppliers always provide detailed QC reports on this tolerance.
7.2. Anti-Friction and Anti-Adhesion Surface Treatment Technology
Prioritize knitting machine needle components with advanced coatings, which determine the needle lifespan and fabric quality:
- DLC (Diamond-Like Carbon) Coating: Maximizes friction reduction, increases yarn gliding capability, reduces heat generation, and extends needle life, while also preventing the adhesion of lint and oil residue.
- Surface Finish: The needle surface must be super smooth (low Ra) for the yarn to glide over without damage and without retaining dirt.
7.3. Core Hardness and Fatigue Strength
The knitting machine needle must be vacuum-hardened to achieve the optimal balance:
- Surface Hardness: High (60–65 HRC) to resist wear from friction.
- Core Toughness: Sufficient to resist brittle fracture when subjected to shocks or cyclic stress repeated millions of times at high speed.
8. Preventive Maintenance Solutions from VieTextile
VieTextile understands that the knitting machine needle is a critical component. We provide high-quality knitting machine needle solutions that help knit manufacturers minimize faults and optimize productivity.
We are committed to supplying genuine knitting machine needle products, manufactured from specialized tool steel alloys, applying DLC coating technology, and adhering to the strictest tolerance standards.
9. Frequently Asked Questions about Knitting Machine Needles (FAQ)
9.1. How often should knitting machine needles be replaced simultaneously?
Answer: The replacement of knitting machine needle components should be based on operating hours (typically 2500 to 3000 hours) or the total weight of fabric produced (e.g., 80–100 tons), even if the needle is not yet broken. Simultaneous replacement according to a Proactive Replacement schedule is the best strategy to prevent vertical fabric stripe faults (Needle Lines) caused by uneven wear between old and new needles.
9.2. What is the function of the DLC (Diamond-Like Carbon) coating on the needle?
Answer: The DLC coating is an advanced surface treatment technology that helps:
- Maximize Friction Reduction: Helps the needle move smoothly in the cylinder slot, reduces heat generation, and minimizes fabric wrinkling and Loop Distortion.
- Increase Lifespan: Enhances surface hardness, resisting wear more effectively than conventional Chrome plating.
- Anti-Adhesion: Prevents the accumulation of oxidized oil residue and lint, reducing the risk of dirty or stained fabric.
9.3. How to distinguish between fabric stripes caused by the needle and those caused by the yarn?
Answer:
- Needle Stripes: Typically clear, vertical stripes, fixed according to the needle column position, appearing continuously and not changing with the yarn batch. The cause is a worn needle or a Butt Height error that changes the stitch length at a specific needle column.
- Yarn Stripes: Often faint, horizontal or vertical stripes, not fixed, which may change or disappear when the yarn batch is changed (due to differences in yarn twist, count, or dye affinity).
9.4. Can a rusted knitting machine needle continue to be used?
Answer: Absolutely not. A rusted knitting machine needle creates rough patches and sharp edges, increasing friction tremendously. When this needle moves, it will scratch, score, and tear the yarn, causing severe Holes and fabric tears. Rust also damages the cylinder slot and adjacent needles.
9.5. What role does lubricating oil maintenance play for the knitting machine needle?
Answer: High-quality lubricating oil is the “lifeblood” of the knitting machine. It has 3 main roles for the needle:
- Friction Reduction: Ensures the needle moves smoothly, reducing fabric wrinkles and extending needle life.
- Cooling: Reduces the heat generated by friction at high speed.
- Cleaning & Anti-Rust: Knitting oil must have the ability to clean lint and dirt particles, while also protecting against oxidation and rust on the needle surface.
- Note: Only use specialized, washable knitting oil to avoid dirty fabric faults.
Please contact us for expert consultation on selecting the appropriate knitting machine needle for your yarn type and machine Gauge, as well as effective preventive maintenance strategies.
Contact Information:
Hotline: 0901 809 309
Email: info@vietextile.com
Website: https://vietextile.com
