Textile Engineering
What the exam tests
The Textile Engineering domain of the PEC Engineering Practice Examination assesses applied knowledge across the fibre-to-fabric chain: fibre identification, yarn numbering, spinning and fabric formation, fabric geometry, and wet processing. Questions are calculation-heavy and ask you to select a process, diagnose a fault, or verify a specification against a standard.
Fibre and yarn basics
Fibres are natural (cotton, flax, wool, silk) or man-made (regenerated viscose and lyocell; synthetic polyester, nylon, acrylic). Identification uses burning behaviour, solubility, and microscopy: cotton burns like paper with soft grey ash, polyester melts and draws a hard bead, and wool smells of burnt hair. Yarn count is determined per ISO 2060 from skein mass at standard regain, so conditioned mass matters.
Count systems
Direct systems give mass per unit length: tex (g/1000 m), dtex, and denier (g/9000 m). Indirect systems give length per unit mass: Ne (840 yd/lb), Nm (m/g), and worsted count. Key conversions are:
- tex = 590.5/Ne
- tex = 1000/Nm
- tex = 885.8/worsted count
- denier = 9 × tex
Spinning selection matters too: combing removes short fibre and neps to make finer, stronger yarns; rotor spinning is productive but less regular at fine counts; air-jet spinning gives low hairiness.
Worked example
A 40 Ne cotton yarn. tex = 590.5/40 = 14.8 tex. Denier = 9 × 14.8 = 133 denier. With a cotton twist multiplier of 4.0, TPI = 4.0 × √40 = 25.3. For a fabric sett of 30 ends/cm × 25 picks/cm, the weft-way cover check uses 25 picks/cm with the calculated yarn tex.
Traps
- Reversing direct and indirect logic: higher Ne means finer; higher tex means coarser.
- Using 1000/Ne instead of 590.5/Ne for cotton.
- Reporting oven-dry mass when the specified count is at conditioned regain.
- Swapping ends/cm (warp) with picks/cm (weft), or wales with courses in knitted structures.