Ring Spinning: Match Drafting, Twist and Traveller Conditions

An end break needs a location and a time

A ring frame can make the correct average yarn count yet suffer repeated end breaks. Those breaks cost production time. The draft ratio may be right, but it cannot show whether fibres remain under control. Nor can it show whether the yarn meets a sharp tension peak as the cop builds.

Start the investigation with two questions: where does the strand fail, and when does it fail? A few positions may cause most breaks. That pattern needs a different first check from a rise across the whole machine. Breaks just after doffing also deserve a separate record from those during steady running.

Ring spinning drafting, twist insertion and winding share one material path. A useful setting trial follows that path and measures the result at each relevant point. It keeps the desired count and end-use quality in view while testing a specific cause.

The calculations below use invented teaching figures. They explain relationships, not approved speeds, roller settings or traveller choices for a particular frame. Ask the machine and component makers for the limits that apply. Check them against the material and a controlled trial.

Follow the strand from roving to cop

The roving package supplies the drafting system. Roller pairs draw the strand out, and aprons help guide fibres through the main drafting zone. The emerging strand gains twist as it forms yarn. It then passes through the yarn guide and traveller. The spindle carries the tube on which the yarn winds.

The ring is supported by the ring rail. The traveller moves around the ring; it is not a small motor with an independent speed command. The winding action depends on relative motion between the rotating package and traveller. Ring-rail motion distributes yarn along the cop as layers build.

These functions explain why the point of failure does not always identify its cause. A weak section created during drafting may break when winding tension rises. Replacing a traveller could reduce that tension, yet leave the weak sections in the delivered yarn.

The reverse is possible too. Good laboratory strength does not rule out a damaged guide or a poor local spinning condition. Keep the yarn results beside the machine record. Both the spinning position and the cop stage matter.

Establish the count before changing the drafting conditions

For one feed strand, the ideal draft is the ratio of feed linear density to delivered linear density. Both must use the same unit. Tex means grams per 1,000 metres; higher tex describes a heavier strand.

Suppose one position receives 600 tex roving and must produce 20 tex yarn. Ignore waste, slip and changes in moisture for this first calculation:

Total draft = 600 ÷ 20 = 30.

A delivered metre contains one-thirtieth of the mass in a metre of feed. This does not mean individual fibres stretch to thirty times their length. They move relative to one another as the strand becomes longer and thinner.

At a front-roller delivery of 20 m/min, the ideal back-roller surface speed is:

Back speed = 20 ÷ 30 = 0.6667 m/min.

Check the mass flow. The feed carries 0.6 g/m × 0.6667 m/min, or about 0.4 g/min. The output carries 0.020 g/m × 20 m/min, also 0.4 g/min. Use unrounded values when checking that balance.

ApparelDiary's yarn count conversion guide helps when a mill sheet mixes tex, metric count and English cotton count. Convert first; a ratio made from different count systems has no useful meaning.

Divide the draft without changing the required count

In a three-line system, define break draft as middle-roller surface speed divided by back-roller surface speed. Main draft is front speed divided by middle speed. The middle speed cancels when these two ratios are multiplied.

For the example, choose an illustrative break draft of 1.20:

Main draft = 30 ÷ 1.20 = 25.

The middle-roller surface speed is then 20 ÷ 25 = 0.8 m/min. The two zones give 0.8 ÷ 0.6667 ≈ 1.20 and 20 ÷ 0.8 = 25.

Suppose a trial changes break draft to 1.30. To retain total draft 30, main draft must become 30 ÷ 1.30 = 23.0769. If main draft stayed at 25, total draft would rise to 32.5. Under the same ideal assumptions, the yarn would become 600 ÷ 32.5 = 18.46 tex.

That unintended count change would weaken the comparison. The trial would have changed both draft distribution and yarn size. A measured fall in breaking force could then reflect the finer yarn as well as any change in fibre control.

Use surface speed, not roller rpm alone

Rollers of different diameters do not deliver the same length at the same rpm. For a circular roller without slip:

Surface speed in m/min = π × diameter in metres × rpm.

A 25 mm roller turning at about 254.65 rpm gives 20 m/min. A speed reading needs its roller diameter and measurement point to be useful. The machine may calculate its delivery reading. Find which diameter and drive ratio it uses, then compare it with a separate measurement.

Fibre control requires more than the right speed ratio

The strand contains fibres of different lengths. Some can bridge key control points. Shorter fibres depend more on the apron system and contact with nearby fibres. Their movement affects where they accelerate toward front-roller speed.

NPTEL's ring-spinning notes explain the role of aprons, spacers and loaded top rollers. An apron opening that is too wide can give poor fibre control. An opening that is too narrow can impose excessive restraint. Roller spacing also matters. It must allow the strand to draft while keeping control of the fibres. Too much restraint can damage long fibres.

This creates a practical limit on generic setting tables. Two materials may produce the same nominal count but differ in other ways. Their fibre lengths, roving twist and surface behaviour may all differ. A setting that works for one need not suit the other.

The Saurer Texparts drafting-systems brochure lists different cradles for different fibre-length ranges. It also ties top-roller and cot choices to the applied system and material. Those distinctions are a reason to identify the installed parts before moving a setting.

A useful drafting check records the weighting arm, cradle, spacer, cot and apron identities together. The team should also know their condition. A worn apron may carry the same part number as a sound one. That does not make their condition equal.

Check the actual approved setting method. A load value at one point in a mechanism is not automatically the nip load at another. A spacer colour identifies a part within a stated system. It does not define the same gap in every system.

Treat a changed waste pattern as evidence

An experimental study by Murugesan and Senthilkumar examined waste collected at the ring-frame drafting system. Its cotton and polyester/cotton trials varied roving hank, break draft, traveller and twist. The reported relationships involved strand width as well as waste.

The study supports asking a wider trial question than whether ends down improved. In a mill trial, collect waste on a stated time and input basis, then assess yarn quality from the same runs. A calmer frame may still be losing useful fibre or making yarn with a different surface.

Do not transfer a research setting directly to another material. The paper helps explain what to observe. The local trial must show whether the proposed setting works.

Separate nominal twist from the winding-speed difference

The familiar machine calculation divides spindle rpm by delivery in metres per minute. With a spindle speed of 16,000 rpm and delivery of 20 m/min:

Nominal twist = 16,000 ÷ 20 = 800 turns/m.

If spindle speed stays fixed and delivery rises to 22 m/min, this nominal value falls to 727.27 turns/m. Delivery has risen by 10%, but nominal twist has fallen by about 9.09%. The two percentage changes are not equal because one quantity is the divisor.

To keep the nominal value at 800 turns/m while delivering 22 m/min would require 17,600 rpm. That arithmetic does not establish that the speed is suitable. It describes the new operating point that a qualified team would have to assess.

Why the traveller runs behind the spindle

The package must take up the yarn being delivered. Hold the winding diameter fixed for a moment. Each relative turn between package and traveller then winds about one circumference of yarn. This gives a simple teaching model:

Delivery = π × winding diameter × (spindle rpm − traveller rpm).

Use diameter in metres and delivery in m/min. This simple model leaves out the winding helix, yarn stretch and slip. It also ignores short-term changes in balloon length. It describes a steady point, not every instant of ring-rail travel.

The twist-mechanism discussion by Gandhi and Stanley distinguishes traveller rotation, winding and subsequent yarn withdrawal. The following values are an independently calculated example of that distinction.

At a 40 mm winding diameter:

Speed difference = 20 ÷ (π × 0.040) = 159.15 rpm.

The traveller therefore runs at about 16,000 − 159.15 = 15,840.85 rpm. Divide that rotation by delivery to get about 792.04 turns/m. This is the model value before yarn withdrawal.

The smaller winding diameter needs a larger relative speed to take up the same length. Winding diameter is the local diameter where yarn is being laid. It is not the ring diameter, and it can change during the build.

Do not call the difference a laboratory twist fault

The nominal 800 turns/m and the model values answer different questions. With over-end withdrawal, the way each coil leaves the package can add or remove twist. The directions of winding and withdrawal must match for this ideal case. The added turns can then restore the nominal spindle-based value.

ASTM D1423/D1423M-16(2022) warns that withdrawal method, tension and specimen rotation affect twist results. Its public guidance gives the side-versus-over-end difference as 1/(πd), with consistent length units. For a 40 mm package, that is about 7.96 turns/m.

So a reported twist result needs its method and sample preparation. Do not change a machine setting just to force a reading toward a number calculated on a different basis. First establish what the laboratory measured and how the specimen left the cop.

Match the traveller to the ring, yarn and spinning conditions

Traveller choice includes shape, wire section, mass and surface finish. Bräcker's traveller brochure explains that the traveller must suit both the ring and yarn. Yarn passage matters: the strand must not become trapped between ring and traveller.

The practical choice is therefore more specific than a count-to-number lookup. Record the full designation and ring profile. Two products may have similar nominal weight but different shapes or surface behaviour.

The Bräcker short-staple manual treats its traveller-size guidance as a starting point for trials. Ring condition, spinning geometry, twist, material and operating conditions can alter the suitable choice. Its yarn-break discussion also separates steady spinning from doffing and restart faults.

That separation helps avoid an unhelpful response to every break. A trial may reduce steady-running breaks but leave restart failures unchanged. The next check should then follow the restart evidence. It should not assume that the same traveller change must solve both.

Ring diameter changes the peripheral speed

The traveller's path speed is its rotations per second multiplied by the path circumference. For an approximate 42 mm running-path diameter at 15,840.85 rpm:

Path speed = π × 0.042 × 15,840.85 ÷ 60 = 34.84 m/s.

Using spindle rpm instead would give about 35.19 m/s. That is a convenient approximation here, but it ignores traveller lag. Neither result is a permitted-speed limit.

The nominal ring size may not equal the exact traveller running-path diameter. Use the maker's basis for a component check. The calculation shows the effect of ring size. At the same rpm, a larger running path gives a higher peripheral speed.

Rieter's G 38 information describes a high-speed package that combines a spindle, smaller ring and matching tube. It also describes model-specific balloon geometry. The parts are designed to work together. Their published maximum speed does not apply to every frame with different parts.

Build a trial around one suspected cause

Suppose breaks rise late in the cop build. The mill suspects its present traveller choice is one cause. It should first confirm the complaint with position and time records. A count of all stops across several shifts would not isolate that claim.

Choose comparable positions and material. Keep the intended count, nominal twist and speed schedule unchanged. Compare the current traveller with one approved candidate. State the expected benefit before testing. Also set the quality and running conditions that the trial must meet.

The comparison needs similar ring condition and traveller age. Both sets need to be in suitable condition. A fresh candidate might beat a worn current set because it is new, not because its type is better. Record any required running-in stage and evaluate the intended normal-running period separately.

Where the machine allows it, assign treatments across comparable sections. Repeat the comparison in another run. Switching treatments between positions can help show whether a result follows the position or the treatment. It must fit the approved installation and operating method.

Use a clearly defined exposure

In this example, each treatment covers 100 spinning positions in service. Observe each group over eight hours of machine running. These hours exclude planned machine shutdowns. They include the brief intervals when a position is down awaiting piecing. There are therefore 800 observed spindle-hours in each group.

Call this an event rate per observed spindle-hour. It is different from the percentage of positions found down during a spot inspection. One counts break events over time; the other describes a state at a particular moment.

The candidate rate is 42 ÷ 800 × 1,000 = 52.5. Compared with 75.0, that is a 30% lower recorded event rate. The figures are hypothetical and do not prove a repeatable benefit.

The time result is less favourable. The fewer breaks took longer to clear. Total lost spinning time therefore rose from 120 to 126 spindle-minutes. The candidate cannot be described as a production gain from its break count alone.

Check the reason for the longer delay. It might reflect piecing difficulty, operator coverage or a different mix of fault types. Repeating the trial under comparable service conditions would help separate those explanations.

Keep the build stage visible

Divide records by relevant cop stages, using the same stage definitions for both groups. A single average can conceal a strong gain in one stage and a loss in another. Record startup breaks separately from later running breaks.

Use actual exposure for each stage. A stage that lasts longer has more chance to accumulate events. Comparing its raw break count with that of a short stage can create a false impression of the risk.

The same principle applies to position groups. If some positions were unavailable, use the actual in-service count over each interval. A denominator based on the full nameplate count would make the observed rate look lower.

A faster delivery changes the meaning of a time-based rate

Consider a separate speed comparison with 800 spindle-hours at each speed. Ignore all lost delivery for this teaching calculation. At 20 m/min, those hours represent 800 × 60 × 20 = 960,000 metres, or 960 km of yarn. Sixty breaks equal 62.5 breaks per 1,000 km.

At 22 m/min, the same exposure represents 1,056 km. Suppose this run records 66 breaks. Its rate is still 62.5 breaks per 1,000 km, but its rate per 1,000 spindle-hours rises from 75.0 to 82.5.

The figures describe unchanged events per delivered length and more events per hour. Both matter. The length basis shows the burden per unit of yarn. The time basis helps assess the demand for piecing. The simple calculation above assumes continuous delivery. In a real trial, measure delivered length or account for down time.

Neither basis proves that the yarn quality is unchanged. Keep the quality tests and actual accepted output beside both rates when judging a speed increase.

Follow repeated failures at one position

If one position repeatedly fails while nearby positions run well, retain that position number in the trial record. An average across the whole section can hide it. After an approved change, see where the pattern remains. Does it follow the roving package, or stay with the spinning position?

That comparison narrows the search without proving the cause. A persistent position problem may need checks of the drafting parts, guides, alignment or spindle assembly. A problem that follows material needs a closer look at that feed. Any inspection or change must follow the machine's approved stop and service procedure.

Avoid combining several repairs before the team records what it found. Several changes made together may restore running. If the team replaces an apron, changes the traveller and moves the roving, it cannot isolate the cause. Record the combined intervention honestly if production needs require it.

Keep yarn quality in the same decision

Take yarn samples from the trial groups and relevant cop stages. Preserve their identities through winding and laboratory preparation. If samples are pooled too early, a weak group can disappear inside an acceptable overall mean.

Check the agreed linear density, twist, mass variation, imperfections and hairiness measures. Include tensile testing on a consistent basis. ASTM D2256/D2256M-21 covers single-strand tensile properties. It distinguishes breaking force from breaking tenacity.

For an original example, a 20 tex yarn breaking at 400 cN has a tenacity of 400 ÷ 20 = 20 cN/tex. A changed yarn breaking at 380 cN but measuring 19 tex has the same calculated tenacity. Its lower force does not, by itself, prove poorer strength per unit linear density.

The changed count still matters to the customer. Equal tenacity does not make 19 tex yarn an acceptable substitute for a specified 20 tex yarn. Report force, count and tenacity together rather than choosing the single value that favours a trial.

Use the full agreed laboratory method. Public standard summaries help identify scope. The full method provides the needed sampling, conditioning and instrument details, as well as the test procedure.

Approve a setting for the full production route

A successful trial needs stable spinning and acceptable yarn. The cop must also perform well in the next process. Fewer spinning breaks bring little value if winding cuts rise or the cop unwinds poorly. A changed yarn property must still meet the customer’s needs.

Compare accepted output over a defined running period, with all relevant losses included once. Keep the speed schedule and count beside the output figure. More kilograms of a coarser yarn are not evidence of faster delivery of the original product.

Finally, retain the tested component identities and material conditions with the result. A later fibre blend, roving change or replacement component may require another check. The trial establishes a workable combination under stated conditions. Another ring frame may need different settings, even when the product seems similar.

References

• NPTEL: ring-spinning machine questions and component functions.

• Saurer Texparts: drafting systems and matched components.

• Murugesan and Senthilkumar: waste collected at the ring-frame drafting system.

• Gandhi and Stanley: spindle monitoring and the twist mechanism, 2020.

• ASTM D1423/D1423M-16(2022): twist by direct counting.

• Bräcker: travellers for short-staple spinning.

• Bräcker: short-staple manual, especially traveller choice and yarn breaks.

• Rieter: G 38 ring-spinning configuration and component packages.

• ASTM D2256/D2256M-21: single-strand yarn tensile properties.