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Mean retention is 84%. The worst splice in the package is at 61%.
Strength Retention
—%
Splice breaking force against the parent yarn
Bulk, Variability & Risk
Retention at the Weakest Splice
—%
Splice to Yarn Diameter
—x
Bulk Added
—%
Weakest Splice Force
—cN
Safety Factor at the Weakest Splice
—x
Strength Given Up
—cN
Splice Length in Yarn Diameters
—x
Splices in the Package
—
Both breaking forces must be measured on the same instrument at the same gauge length and in the same conditioned atmosphere; a splice tested at a shorter gauge length than the yarn will flatter the retention. The weakest-splice estimate uses three standard deviations below the mean as a practical worst case, which assumes an approximately normal splice strength distribution - real splice populations are often left-skewed with occasional very poor joints, so the true worst case in a large package is likely below this. Splice diameter should be measured optically at the thickest point rather than averaged along the joint. Splices per package is used here only to describe the population; the calculation is per splice and does not compound risk across the package.
Using this calculator
About the Yarn Splice Strength Retention, Bulk & Weakest-Splice Risk
The formula
This is the expression the tool evaluates. Every term is named underneath, with the unit it must be supplied in.
The headline splice specificationretentionPercent = spliceStrength / yarnStrength x 100
Splices are specified as a percentage of parent yarn strength because that is what downstream processing cares about. Eighty per cent is the usual minimum, and a splicer that cannot reach it on a given yarn needs a different setting or a different jointing method.
The other half of the specificationdiameterRatio = spliceDiameter / yarnDiameter bulkIndex = ( diameterRatio - 1 ) x 100
A strong splice that is half as thick again will still show as a slub in a plain fabric and may not pass a heald or a needle cleanly. The two criteria are independent and both have to be met.
The splice that actually failsweakestSplice = spliceStrength x ( 1 - 3 x spliceStrengthCv / 100 )
Splice strength varies far more than yarn strength, because it depends on how well each individual joint formed. Taking three standard deviations below the mean gives a practical worst case for the population in one package.
Margin where the yarn is weakestsafetyFactorAtSplice = weakestSplice / downstreamTension
The splice is the designed weak point, so the margin that matters is this one and not the yarn margin. A warp end carrying twenty splices through a loom is tested at this value every time one reaches the shed.
Symbols used above
Symbol
Stands for
Unit
retention
Splice strength as a percentage of parent yarn strength
%
CV
Coefficient of variation of splice strength
%
bulk
Diameter increase at the splice
%
How the result is derived
Step by step, from the values you type to the figure on screen.
The 8 inputs are read from the form on every keystroke: Yarn Breaking Force, Splice Breaking Force, CV of Splice Strength, Downstream Running Tension, Yarn Diameter, Splice Diameter, Splice Length and Splices per Package.
Each value is checked against the accepted range in the input table below. A value outside its range stops the calculation rather than producing a misleading figure — the results blank out and a message appears.
The validated values are substituted into the expression above, which resolves Strength Retention together with every supporting figure in one pass — no value is carried over from a previous entry.
The supporting outputs — Retention at the Weakest Splice, Splice to Yarn Diameter, Bulk Added, Weakest Splice Force, Safety Factor at the Weakest Splice, Strength Given Up, Splice Length in Yarn Diameters and Splices in the Package — come from the same pass, so they always describe the same case as the headline figure.
Results are rounded for display only. The full-precision value is used throughout the chain, so reading a rounded intermediate figure back into the tool by hand can shift the last digit.
What each input means
Where to read each value on the floor, the unit it must be in, and the range the tool accepts.
Input
Unit
Accepted range
Default
What it means
Yarn Breaking Force
cN
20 to 5000 cN
320
Splice Breaking Force
cN
10 to 5000 cN
268
CV of Splice Strength
%
1 to 40 %
9
Downstream Running Tension
cN
1 to 2000 cN
58
Yarn Diameter
um
30 to 2000 um
173
Splice Diameter
um
30 to 3000 um
210
Splice Length
mm
5 to 80 mm
22
Splices per Package
—
1 to 300
24
What the tool returns
The headline figure and every supporting value it is built from.
Output
Unit
What it tells you
Strength Retention (headline result)
%
Splice breaking force against the parent yarn
Retention at the Weakest Splice
%
Splice to Yarn Diameter
x
Bulk Added
%
Weakest Splice Force
cN
Safety Factor at the Weakest Splice
x
Strength Given Up
cN
Splice Length in Yarn Diameters
x
Splices in the Package
—
Worked example
Given
0
Yarn breaking at 320 cN, splice at 268 cN with a 9% CV
1
Yarn 173 um across, splice 210 um, 22 mm long
2
24 splices per package, downstream tension 58 cN
Substituting
retention = 268 / 320 = 83.75%weakest = 268 x (1 - 3 x 0.09) = 268 x 0.73 = 195.64 cNweakestRetention = 195.64 / 320 = 61.14%diameterRatio = 210 / 173 = 1.2139, so bulk = 21.39%
Answer
0
Mean retention 83.75% - above the 80% threshold
1
Weakest splice 195.64 cN, a retention of 61.14%
2
Diameter ratio 1.214, so 21.39% bulk added
3
Safety factor at the weakest splice 3.37
4
Splice is 127.17 yarn diameters long
The mean passes comfortably and the worst splice in the package is at 61% of yarn strength. That gap is the whole reason splice CV is specified alongside splice strength - a splicer with a good mean and poor consistency puts a genuinely weak joint into every package, and the mean will never show it.
How to use it
Work through the input groups in order — Strength and Geometry & Package. The defaults are a realistic case, so you can change one value at a time and watch what moves.
There is no calculate button. Every figure recalculates as you type or drag, which is what makes this usable for a what-if sweep rather than a single answer.
Read Strength Retention in the dark results panel — that is the headline figure, expressed in %.
Check the supporting rows underneath (Retention at the Weakest Splice, Splice to Yarn Diameter, Bulk Added, Weakest Splice Force, Safety Factor at the Weakest Splice, Strength Given Up, Splice Length in Yarn Diameters and Splices in the Package) before acting on the headline — they are where an implausible input usually shows itself first.
Reset to defaults returns every field to the reference case, which is the quickest way to check whether a surprising result came from the tool or from an input you had changed earlier.
Where this is used
Process planning — establishing Strength Retention before a trial is booked, so machine time and material in Spinning, Winding & Yarn Package Engineering are committed against a calculated figure rather than an estimate.
Costing and quotation — Strength Retention is an input to the cost sheet, and quoting from a worked number rather than a remembered one is what keeps a margin intact.
Troubleshooting — when the floor result drifts from plan, entering the measured values (starting with Yarn Breaking Force) shows how much of the gap in Strength Retention each variable explains.
Teaching and study — the accepted ranges bracket normal Spinning, Winding & Yarn Package Engineering practice, so moving one variable at a time shows the shape of the relationship rather than a single answer.
Reading the result
Typical bands and what each one is telling you.
Value
What it indicates
Above 85% retention
Excellent splice. Well-set splicer on cooperative yarn.
75 - 85%
Normal commercial range; 80% is the usual contractual minimum.
Diameter ratio under 1.2
Acceptable bulk for most woven and knitted fabrics.
Splice CV above 15%
Inconsistent splicing. Check air pressure, opening time and chamber wear.
Assumptions and limits
Both breaking forces must be measured on the same instrument at the same gauge length and in the same conditioned atmosphere; a splice tested at a shorter gauge length than the yarn will flatter the retention. The weakest-splice estimate uses three standard deviations below the mean as a practical worst case, which assumes an approximately normal splice strength distribution - real splice populations are often left-skewed with occasional very poor joints, so the true worst case in a large package is likely below this. Splice diameter should be measured optically at the thickest point rather than averaged along the joint. Splices per package is used here only to describe the population; the calculation is per splice and does not compound risk across the package.
Every input is bounded to the range normal practice occupies (Yarn Breaking Force 20 to 5000 cN, Splice Breaking Force 10 to 5000 cN and CV of Splice Strength 1 to 40 %, and so on for the rest). Those bounds are guard rails against typing errors, not a claim that the formula fails one unit outside them.
The calculation is deterministic: the same inputs always give the same result. It carries no allowance for machine condition, operator skill, ambient conditions or lot-to-lot material variation unless an input above explicitly represents one.
Nothing is sent anywhere. The maths runs in your browser, so the numbers you type never leave the page.
Standards and further reading
ISO 2062 - Determination of single-end breaking force, applied to both yarn and splice.
ASTM D2256 - Tensile Properties of Yarns by the Single-Strand Method.
USTER splice classification, for the appearance grading that accompanies the strength test.
Questions people ask
Why is 100% retention not achievable?
Because a splice reassembles fibres that were cut, without twist continuity across the joint. A pneumatic splicer opens both ends, intermingles the fibres in a compressed-air chamber and lets the yarn twist bind them, but the fibres crossing the joint are fewer and less well oriented than in the parent yarn. Eighty to ninety per cent is the practical ceiling for staple yarn; filament splices can do better, and a knot does worse on bulk while doing better on strength.
Should splice strength CV be specified as well as the mean?
Yes, and it is the more useful of the two for predicting trouble. The mean tells you whether the splicer is capable; the CV tells you whether it is reliable, and downstream failures come from the tail rather than the middle. A splicer at 85% mean with 5% CV puts a worst splice at 72%; the same mean at 15% CV puts it at 47%. Only the second one will cause loom stops, and the two look identical on a mean-only specification.
Splices pass the strength test but cause loom stops. Why?
Usually bulk rather than strength. A splice 20% thicker than the yarn has to pass through a drop wire, a heald eye and a reed dent on every pick, and abrasion against those is a different failure mode from tensile break. It is also worth checking splice appearance grading rather than only strength - a splice that is strong but has protruding fibre ends will catch where a smooth one of the same strength does not.
