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Formulas/Calculations

Statistical Quality Control in Textiles

Formulas/Calculations Quality Management & Inspection Textile School / July 23, 2025 / Leave a Comment

This document offers a comprehensive guide to Statistical Quality Control (SQC) in textiles, detailing essential calculations for monitoring and improving process and product quality. It covers formulas for Coefficient of Variation (CV), control chart limits, chi-square test, F-test, Process Capability Index (Cpk), Defects Per Million Opportunities (DPMO), and Acceptance Quality Limit (AQL) sampling. Supported by derivations and practical examples, this resource is tailored for textile engineers, quality control professionals, and production managers to ensure consistent quality and compliance with industry standards.

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Testing & Quality

Replicate Statistics for a Lab Result

Fabric Testing Quality & Testing Quality Management & Inspection Textile School / August 28, 2026

Turns the readings from a set of test specimens into the mean, sample standard deviation, CV% and a confidence interval built on the correct t value for the specimen count – the summary every textile test report has to carry, whatever property was measured.

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Testing & Quality

Restricted Substance Limit: Result, Uncertainty & the Next Limit

Fabric Testing Quality & Testing Quality Management & Inspection Textile School / August 26, 2026

Places a laboratory result against a restricted substance limit with its expanded uncertainty, applies a guard band to give an acceptance limit, converts the result between mg/kg, ppb and percent, and reports the margin against a later limit that a stepped-down threshold will bring.

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Testing & Quality

Fibre Content Label: Declared Blend, Test Result & Tolerance

Fabric Testing Quality & Testing Quality Management & Inspection Textile School / August 26, 2026

Compares a declared fibre composition against a test result fibre by fibre, applies the tolerance as percentage points of total fibre weight rather than as a percentage of the declared figure, shows the band each declaration allows, and removes the tolerance where the label claims a single fibre.

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Mill Operations & Industrial Engineering

Mill Water Balance against a Specific-Consumption Benchmark

Machinery & Mill Operations Mill Operations & Maintenance Quality & Testing Quality Management & Inspection Textile School / August 19, 2026

Separates process demand from fresh intake through the recycle loop, closes the balance across evaporation, effluent and discharge, and compares specific consumption against a benchmark to give the saving available and the recycle rate that would match it.

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Mill Operations & Industrial Engineering

Boiler Heat Balance, Blowdown Loss & Flash Recovery

Machinery & Mill Operations Mill Operations & Maintenance Quality & Testing Quality Management & Inspection Textile School / August 19, 2026

Builds the boiler heat balance from steam demand and feedwater temperature, adds the blowdown heat loss, converts the total to fuel and cost per tonne of steam, and returns the make-up water and the flash steam a condensate return would yield.

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Testing & Quality

Seam Slippage against Cloth Cover Factor

Fabric Testing Quality & Testing Quality Management & Inspection Textile School / August 19, 2026

Computes warp, weft and Peirce cloth cover factors from sett and count, takes the worse of the two measured slippage forces against specification, and solves the cover factor and pick density a target resistance would actually require.

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Testing & Quality

Overall Moisture Management Capability from MMT Indices

Fabric Testing Quality & Testing Quality Management & Inspection Textile School / August 19, 2026

Normalises the three moisture management tester outputs onto their index scales, blends them into the OMMC with the standard weighting, returns the grade, and identifies which index is limiting and what perfecting it alone would be worth.

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Testing & Quality

Blue Wool Lightfastness Rating from Exposure

Fabric Testing Quality & Testing Quality Management & Inspection Textile School / August 19, 2026

Places measured exposure hours on the logarithmic blue wool scale, returning the achieved rating and the standard it rounds to, the hours a target grade demands, the margin either way and the equivalent AATCC fading units.

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Mill Operations & Industrial Engineering

Industry 4.0 Maturity: Weighted against Constrained

Machinery & Mill Operations Mill Operations & Maintenance Quality & Testing Quality Management & Inspection Textile School / August 19, 2026

Scores digital maturity two ways – the weighted average an assessment usually reports and the minimum the dependency chain actually permits – and reports the overstatement between them, the limiting layer and the levels of investment a target implies.

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Quality Management & Inspection

Statistical Quality Control in Textiles

Replicate Statistics for a Lab Result

Restricted Substance Limit: Result, Uncertainty & the Next Limit

Fibre Content Label: Declared Blend, Test Result & Tolerance

Mill Water Balance against a Specific-Consumption Benchmark

Boiler Heat Balance, Blowdown Loss & Flash Recovery

Seam Slippage against Cloth Cover Factor

Overall Moisture Management Capability from MMT Indices

Blue Wool Lightfastness Rating from Exposure

Industry 4.0 Maturity: Weighted against Constrained

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