Maintaining Precision in Double Jersey Circular Knitting Machines

Double jersey circular knitting machines are integral to the global textile manufacturing sector, widely valued for their ability to produce complex fabric structures with excellent elasticity, durability, and visual appeal. However, consistent high-quality output demands strict mechanical precisionparticularly in the machines circular degree and flatness. Any deviation in these parameters can compromise fabric quality, reduce productivity, and lead to premature wear on critical components.

This comprehensive guide explores the most common mechanical issues faced in double jerseycircular knitting machinesspecifically chain wheel abrasion and cylinder flawsand provides systematic methods for inspection, analysis, and correction to maintain optimal performance.

At the heart of adouble jersey circular knitting machinelies a system of rotating componentscylinders, dials, chain wheels, and traysworking in harmony to form consistent, high-quality knit patterns. The "circular degree" refers to the roundness of these rotating components, while "flatness" indicates the evenness of the working surfaces. Together, these characteristics determine how smoothly and accurately the machine operates.

Maintaining a precise circular degree (ideally less than 0.03 mm deviation) and high flatness (less than 0.05 mm variation) ensures even needle movement, reduces stress on moving parts, and enhances fabric uniformity. When neglected, issues like chain wheel wear and cylinder deformation can lead to irregular loop formation, pattern distortion, machine vibration, and mechanical failure.

Chain wheels play a crucial role in transmitting rotational motion within circular knitting machines. Over time, due to constant friction and mechanical load, these components can suffer abrasionmanifesting as looseness, misalignment, or increased backlash between the chain wheel and its mating parts.

Irregular or uneven rotation of the tray.

Increased noise or vibration during operation.

Inaccurate stitch formation.

Loosening of the drive system.

To evaluate the extent of chain wheel abrasion and its impact on machine precision, follow this step-by-step inspection process:

Stop the machine and ensure all moving parts are in a stable state.

Place a dial indicator on the needle plate bracket to measure precision displacement.

Use a gauge stand to isolate movement by positioning it on non-operating machine components.

Manually push and pull the chain wheel and tray while observing the dial indicator's reading.

Interpreting Results:

Variation <0.001 mm: Excellent precision.

Variation 0.01 mm 0.03 mm: Acceptable range; minor wear may be present.

Variation >0.05 mm: Significant wear; immediate corrective action is required.

If the inspection confirms chain wheel wear beyond acceptable limits, take the following steps:

Loosen fastening screws to release the cylinder and dial assembly.

Regulate and realign the cylinder and dial to achieve a circular degree variation of less than 0.03 mm.

Check and correct flatness:

If deviation exceeds 0.05 mm, insert precision spacers between contact surfaces to adjust the alignment.

Repeat measurement until flatness falls within the acceptable range.

Inspect for physical flaws on the chain wheel or tray surfaces (cracks, dents, worn teeth) and record circular degree data for reference.

Replace components if wear is too extensive for adjustment.

Even after addressing chain wheel issues, precision problems may persistoften rooted in the machine's cylinder. The cylinder, which houses the vertical needle movement system, is central to loop formation. Any ovality or surface flaws here will directly impact knitting quality.

Persistent irregular circular degree measurements after chain wheel adjustment.

Oval shape or egg-shaped deviations in the cylinder.

Localized irregularities in knitting or misaligned needles.

If circular degree remains greater than 0.05 mm even after external factors like chain wheel abrasion are resolved, further diagnosis is necessary.

Analyze degree data across multiple contact points around the cylinder.

Compare the variation:

If differences between opposite points are consistently <0.02 mm, the cylinder likely has an oval shape.

If the shape is generally round but has localized deviations, this points to surface flaws or dents.

Loosen the mounting screws securing the cylinder and dial assembly.

Readjust the cylinder alignment to reduce circular deviation to under 0.03 mm.

Measure and regulate flatness:

Insert spacers as needed to reduce flatness deviation to under 0.05 mm.

Ensure that adjustments do not create additional tension or imbalance.

Loosen the cylinder header (after flatness regulation) to relieve internal stress.

This step is critical in maintaining long-term alignment stability.

Confirm that both cylinder and dial remain relaxed (i.e., free from internal tension or distortion).

Once flatness and alignment are addressed, the final step is fine-tuning the circular degree to ensure sustained performance. This regulation process helps neutralize external forces and compensates for any misalignments introduced during maintenance.

Maintain the dial indicator on the cylinder, pointing precisely at the contact surface.

Adjust the tray laterally (left and right) while monitoring changes on the dial indicator.

Insert or remove spacers to correct minor deviations.

Loosen the located block, allowing for more flexible adjustment of the circular degree.

Ensure that adjustments stay within the tray's design limits to avoid overextension or misalignment.

Gradually eliminate external forces (such as tension from surrounding components), then retighten the located blocks to lock the new alignment.

Repeat measurements to confirm stability of circular degree and flatness after final locking.

Always use high-precision dial indicators and calibration tools.

Record all data points before and after adjustment for quality control and traceability.

Inspect other related components (e.g., needle tracks, sinker plates, cams) for wear that may affect precision.

Perform regulation in a clean environment to avoid introducing particles or contaminants.

Precision in textile manufacturing is not achieved through design aloneit requires ongoing maintenance, regular inspections, and a clear understanding of how mechanical deviations affect production. By addressing chain wheel abrasion and cylinder flaws early, operators can:

Improve fabric quality consistency.

Extend machine service life.

Reduce downtime caused by unscheduled repairs.

Minimize material waste and operational costs.

Enhance overall production efficiency and customer satisfaction.

Double jersey circular knitting machinesare marvels of engineering that offer versatility and efficiency when properly maintained. However, even minor deviations in circular degree or flatness can compromise product quality and production stability. By systematically inspecting for chain wheel abrasion and cylinder flaws, and regulating circular degree using precision tools and techniques, manufacturers can ensure these machines perform to their full potential.

This guide provides a foundation for establishing a preventative maintenance routine and developing troubleshooting protocols in textile manufacturing environments. With consistent attention to mechanical precision, your double jersey knitting operations can remain reliable, efficient, and competitive in todays demanding textile market.