Yarn Realisation in Spinning: Reconcile Fibre Input, Waste and Saleable Yarn

Two spinning reports can show different yarn realisation figures even when the mill has lost the same amount of fibre. One report may include yarn waiting for release. Another may use wet bale weights against drier yarn. A third may count material twice when soft waste returns to the mixing.

The division is simple. The hard part is deciding what the two weights represent.

A useful yarn realisation report answers three questions: how much material was consumed, how much became acceptable yarn, and where the rest went. It also separates a physical loss from a gap in the records. Without those distinctions, a higher percentage can hide more second-grade yarn or a change in moisture.

The examples below are invented to show the calculations. Their yields, prices and waste rates are not targets for a particular mill. Each example states its own boundary so that the result can be checked before it is used.

Define the yarn and material being compared

Yarn realisation is the mass of yarn obtained from a stated mass of material consumed, expressed as a percentage:

Yarn realisation (%) = yarn output ÷ material consumed × 100

Both masses must use the same unit and a consistent moisture basis. The records must also cover the same process and period. A mixing-room issue cannot be compared directly with dispatch if finished yarn stock rose during the month.

Choose the output point first. For a mill that makes packed cones, the useful endpoint may be net yarn accepted into finished stock. Dispatch then becomes a separate stock movement. For a mill that sells cops, the boundary may end before winding. These reports answer different questions, so their results should carry different labels.

The numerator also needs a quality rule. Record first-quality yarn separately from yarn accepted for sale at a lower grade. Material still awaiting a decision should stay in a held-stock category until its status changes. Calling it good output early makes the current period look better and leaves the next period to absorb any rejection.

For a defined process boundary, calculate net consumption as:

Net consumption = external material entering + opening process stock − closing process stock

Here, process stock includes material inside the boundary that has not yet reached an output category. It may include fibre, sliver, roving, cops awaiting winding, held yarn and reusable waste awaiting return. Define the categories so that no kilogram appears in two places.

External feed includes any purchased reclaimed fibre used by the process. It need not be virgin cotton. By contrast, a transfer between two departments inside the boundary is not new external feed.

Keep the sales account alongside the physical account. A buyer may pay on an agreed commercial mass, while the process balance uses measured dry mass. Both can be valid for their stated purpose, but combining one input basis with another output basis makes the yield hard to interpret.

A complete dry-mass balance

Consider one period in a fictional carded-yarn mill. All figures have been put on a consistent dry-mass basis. Opening and closing stock include the reusable material and held yarn within the chosen process boundary. There are no unlisted transfers across that boundary.

The mill receives 10,000 kg of external feed into the process. It starts with 600 kg in process and ends with 800 kg. Net consumption is therefore:

10,000 + 600 − 800 = 9,800 kg

Its output and measured waste account is as follows.

First-quality yarn realisation is 8,624 ÷ 9,800 × 100, or 88.0%. Total accepted yarn realisation is 8,820 ÷ 9,800 × 100, or 90.0%. Neither result should replace the other. The two-point gap shows how much accepted yarn entered the lower grade.

The complete balance also closes:

600 + 10,000 = 800 + 8,624 + 196 + 882 + 98 = 10,600 kg

Dividing first-quality yarn by the 10,000 kg issued would give 86.24%. That calculation ignores the 200 kg increase in process stock. It makes stock accumulation look like a loss of conversion yield.

The 98 kg residual is still unexplained. It might include uncollected fly, a stock estimate error, missed waste entries or errors in moisture correction. The arithmetic alone cannot assign a cause. Leave it visible while the records are checked; do not spread it across waste categories merely to close their totals.

Dry mass also needs a precise meaning. Dry cotton feed can contain dry trash and other non-fibre matter. A dry-mass yield is therefore not automatically a measure of how much pure cellulose was retained. To answer that question, the composition of both feed and removed waste would also need to be known.

Separate water changes from material recovery

Moisture regain and moisture content use different denominators. Regain expresses water mass relative to dry material. Moisture content expresses water mass relative to the total moist material. A number without its definition is not enough for a correction.

For regain expressed as a decimal:

Dry mass = moist mass ÷ (1 + regain)

For moisture content expressed as a decimal:

Dry mass = moist mass × (1 − moisture content)

Thus, 8% regain corresponds to 0.08 ÷ 1.08 × 100, or about 7.41% moisture content. Substituting 8% into both formulas would give different dry masses.

Take a second, separate example. A process uses 1,000 kg of dry feed and makes 900 kg of dry yarn. Feed regain is 8%, while yarn regain is 6% when weighed.

The moist-weight ratio is 954 ÷ 1,080 × 100, or 88.33%. The dry-mass yield is 90.00%. If the same yarn later reaches 8% regain, its moist mass becomes 972 kg. The moist-weight ratio then rises to 90.00%, although the amount of dry yarn is unchanged. The extra 18 kg is water in this example.

This is a balance illustration, not advice to add moisture to meet a yield target. Actual moisture also affects processing and test results. ASTM D2495-07(2024) covers oven-drying measurements for raw cotton, cotton in process and cotton waste. Its public scope also notes conditions for applying the method to blends.

Use a method suited to the material and purpose. ASTM D2654-22 distinguishes several moisture procedures. It also warns that an oven mass loss may include substances other than water. Where that is possible, do not label the full loss as water without evidence. The published scope is a guide to method selection, not a substitute for the full test procedure.

Take moisture samples that represent the weighed lots, and protect them from change before testing. A sample left open in the laboratory may no longer represent the material when it crossed the scale. ApparelDiary's moisture regain and receiving-weight guide explains the same denominator distinction for received fabric; the stock boundary here remains the spinning process.

Give each waste stream a physical meaning

A single total-waste figure can hide very different events. Removed trash is not the same as usable fibre leaving with the trash. Nor does a kilogram of tangled yarn have the same history as a kilogram removed near the start of opening.

Keep the categories tied to actual collection points. A practical account might separate blowroom waste, card waste, comber noil where relevant, hard yarn waste and other collected waste. Record clean material held for reuse separately from material that has left the process for sale or disposal.

The SITRA technical note in its 2022 e-Techletter discusses the extra conversion cost already carried by hard waste. It also treats stock estimates, weighing errors and moisture differences as possible contributors to an unexplained balance. These are reasons to investigate the location and cause of a loss, rather than value all missing mass alike.

An original trial illustrates the point. Suppose two settings each remove 20 kg of dry waste from the same amount and type of feed. One waste sample contains a larger share of usable fibre. Equal waste weights do not establish equal cleaning performance. The remaining material must also be checked for trash, fibre damage and the quality needed downstream.

Equipment can help distinguish good fibre from unwanted matter. Trützschler describes optical waste monitoring for this purpose and a separate system for recovering cotton from certain waste streams. These are manufacturer descriptions of specific equipment. They do not establish the recoverable share or financial gain in another mill.

Use your own representative waste samples and a suitable analysis method. Look at the whole shift or trial, not just the clean handful that is easiest to collect. Also record where the sample came from. Material drawn from a combined filter cannot, by itself, identify which card or opening machine produced it.

Do not count internal returns as fresh input

Soft waste can leave a machine and later re-enter the process. This creates a second pass through equipment, but it does not create new material at the mill boundary.

Assume a closed trial receives 1,000 kg from outside its boundary. During processing, 100 kg is diverted and returned once. The trial finishes with 900 kg of accepted yarn and 100 kg of external waste. There is no opening or closing stock change.

The overall yarn yield is 900 ÷ 1,000 × 100, or 90%. Counting the returned 100 kg as another external input would give 900 ÷ 1,100 × 100, or 81.82%. That would mix a measure of gross machine load with a measure of material conversion.

Gross load can still matter. The extra pass uses machine time and may add handling or quality risks. Record it as reprocessing activity alongside the external mass balance. A good external yield can coexist with a large volume of repeated work.

Returns held at period end belong in closing stock if they remain inside the defined boundary. If one department sells or transfers material to a separate operation, both parties need matching transfer records. The receiving operation then has an external input of its own.

Do not assume that all material called soft waste can return to the same mixing. Fibre identity, cleanliness, colour, damage and the yarn specification still constrain its use. The balance records where material went; it does not approve a reuse route.

Put departmental percentages on one basis

Departmental waste rates often use the feed to that department as their denominator. Adding them directly can give the wrong overall loss. This is especially easy to miss when several small percentages look close enough to add.

Consider a simple line with no internal returns or stock changes. It starts with 1,000 kg. The three fictional losses below are each measured against the material entering that stage.

Overall yield is 936.341 ÷ 1,000 × 100 = 93.6341%. The same result follows by multiplying the stage yields: 0.98 × 0.97 × 0.985 × 100.

Subtracting 2 + 3 + 1.5 from 100 would give 93.5%, which uses the wrong base for the later losses. On the original-input basis, the losses are 2.0000%, 2.9400% and 1.4259%. Those figures can be added because their denominator is common.

Write the denominator beside every reported waste rate. A noil percentage on comber feed cannot be inserted unchanged into a bale-to-yarn balance. Nor should the simple chain above be applied to a plant with return loops without accounting for those loops.

Protect the yarn specification during yield trials

Reducing the mass removed is useful only if the retained material can still make acceptable yarn. Set the yarn quality requirements before changing a process. Otherwise, a trial can be called successful after the acceptance criteria have quietly moved.

Combing makes the tradeoff clear. Rieter's E 90 product information describes control of noil extraction within that machine's operating range. A listed adjustment range is equipment capability. It is not a recommended noil setting for every cotton, yarn count or end use.

For matched trials, use comparable feed, yarn count, spinning route and output quality requirements. Keep enough material to link preparation results with yarn made from that material. A brief improvement at the card may disappear after later stages are included.

Fibre tests can help explain what changed. Uster's AFIS 6 information describes measures such as fibre length, short-fibre content, fineness, maturity and neps. These measurements answer different questions from a waste scale. They can show whether a lower waste weight accompanies an unwanted change in the retained material.

Check the instrument's sample limits. The February 2025 AFIS 6 technical sheet permits comber noil but excludes blowroom and card-flat waste. It would be wrong to send every waste sample through that instrument simply because it tests cotton.

Yarn acceptance may need several tests. Uster's laboratory services overview lists separate capabilities for mass variation, imperfections, hairiness, strength and other properties. Select the tests required by the product specification, then compare both average results and meaningful variation. One favourable strength result does not prove that all quality requirements have been met.

Record actual yarn count as well. A trial that produces a different count changes the product being compared. ApparelDiary's yarn count conversion guide helps keep Ne, Nm and direct-count units consistent in those records.

Investigate a small residual before promising a gain

Net yarn weight excludes cones, tubes, bags and other packaging. Recheck tare when packaging changes, and use weights that represent the items actually packed. A fixed tare copied from an old cone type can create a steady bias across a large shipment.

A scale display also gives less information than it seems. Its smallest displayed increment is not its full measurement uncertainty. The NIST guide on balances and scales discusses repeatability and other uncertainty sources. Checks should reflect the loads and conditions in use, rather than rely only on the number of decimal places displayed.

Process stock can be a larger concern than scale resolution. Return to the 9,800 kg consumption example. If the closing-stock estimate changes by 50 kg, consumption changes by the same amount in the opposite direction. The calculated first-quality yield would range from about 87.55% to 88.45% across those two assumed stock estimates.

That range is a sensitivity check, not a statistical confidence interval. It shows why a claimed improvement of a few tenths of a point needs a sound stock estimate. Better counting and representative moisture samples may clarify the result before any machine adjustment is justified.

Review both individual periods and their combined balance. Combining periods reduces the influence of the stock counted at the shared boundary. It does not repair missed transfers or a scale that is consistently biased.

Convert a verified gain into a realistic cost effect

Use a fixed amount of acceptable yarn when comparing material requirements. This keeps a production-volume change from being mistaken for better conversion.

In an invented proposal, a mill needs 12,000 kg of acceptable dry yarn. Verified yield would rise from 87.5% to 88.2%, with the same product and quality. Required dry feed would be:

At 87.5%: 12,000 ÷ 0.875 = 13,714.29 kg

At 88.2%: 12,000 ÷ 0.882 = 13,605.44 kg

The saving is about 108.84 kg of feed. The yield rises by 0.7 percentage points. Feed demand falls by about 0.79% relative to the original requirement. These are different measures, so label each one.

Suppose feed costs 2.40 currency units per kg and the displaced waste would have sold for 0.60 per kg. For this simplified case, all material outside acceptable yarn is saleable waste at that rate, with no stock change or unexplained loss. The net material benefit is:

(12,000 ÷ 0.875 − 12,000 ÷ 0.882) × (2.40 − 0.60) ≈ 195.92 currency units

If the change adds 90 currency units of operating cost, the remaining benefit is about 105.92. Actual decisions may need several waste prices, labour, energy, maintenance and quality costs. A reduction in valuable noil sales is not the same as a reduction in low-value sweep waste.

Supplier savings examples also have boundaries. Rieter's air-jet system case states a yarn application and economic assumptions for its comparison. Treat such a case as evidence about that stated comparison. Use your own accepted output, material prices and operating conditions before drawing a mill-wide savings conclusion.

Check whether the product mix explains the average

A mill-wide percentage can move because the proportions of its products have changed. Before attributing that movement to better settings, compare the same product families on the same basis.

Suppose two fictional yarn routes have different yields. Route A consumes 1,000 kg and produces 930 kg of accepted yarn, giving 93%. Route B consumes 9,000 kg and produces 7,650 kg, giving 85%. All masses use one dry basis, with stock changes already included.

The combined result is:

(930 + 7,650) ÷ (1,000 + 9,000) × 100 = 85.8%

Taking the simple mean of 93% and 85% would give 89%, which gives the small route too much weight. In this example, Route B consumes nine times as much material as Route A.

Now suppose the next period splits the same 10,000 kg of feed equally between the routes. Each route keeps exactly the same yield. Accepted yarn becomes 4,650 + 4,250 = 8,900 kg, and the overall result rises to 89%. The 3.2-point increase comes entirely from the changed mix. Neither route has become better at converting its feed.

These fictional rates are not standards for carded, combed or any other named yarn. They show how weighting works. Keep the overall result for material planning, then use matched product comparisons to assess process changes. If a new order changes the yarn count, blend or quality requirement, start a distinct comparison instead of forcing it into an old target.

The same care applies to a trial that runs across a period boundary. Identify which yarn came from the trial feed, including material held in preparation when the setting changed. Running a setting for one shift does not mean that all yarn packed during that shift belongs to the trial. Follow the material through to the agreed output point before calculating its result.

What belongs in the final mill report

A useful report lets another person rebuild the result. Include the period, process boundary, quality definition, moisture basis, external feed, opening and closing stock, yarn grades, measured waste and unexplained balance. Keep source weights available behind each total.

Add the reason for any change from the prior period. A new mixing, a different yarn count and a changed stock estimate can each move realisation without the same operational meaning. Where several yarn types are combined, calculate the total from their masses. Do not take a simple average of percentages from unequal feed quantities.

Finally, connect the reported gain to its evidence. Show that the material balance is credible, the yarn still meets its requirements and the cost comparison includes the waste value that was lost. Those checks turn a percentage into a useful production decision.

References

• ASTM D2495-07(2024): Moisture in Cotton by Oven-Drying.

• ASTM D2654-22: Moisture in Textiles.

• SITRA e-Techletter, 2022: yarn realisation and waste-control notes.

• Trützschler: Sustainable Technologies.

• Rieter: Comber E 90.

• Uster: AFIS 6.

• Uster: AFIS 6 Technical Data, February 2025.

• Uster: Laboratory Testing Services.

• NISTIR 6919: Recommended Guide for Determining and Reporting Uncertainties for Balances and Scales, 2002.

• Rieter: Air-Jet Spinning System.