AiVibeTextile & Automotive Manufacturing
Yarn Twist (TPI, TPM, S and Z)
Yarn twist is the number of turns inserted per unit length to bind fibres together, given in turns per metre or per inch, with direction described as S or Z twist according to the slope of the fibre spiral.
In staple yarns, twist creates the inter-fibre pressure and friction that give the yarn strength. It is expressed as turns per metre or turns per inch, and its direction as S or Z, depending on whether the spiral slopes like the centre of the letter S or Z. Twist multiplier, or twist factor, relates twist to count so that yarns of different fineness can be given comparable twist character; for cotton count, turns per inch equal the twist multiplier times the square root of Ne.
Twist is chosen to suit the end use. Warp yarns usually receive more twist than weft yarns to withstand weaving stresses, knitting yarns are usually given lower twist for softness, and very high twist is used for crepe effects. Ply yarns are commonly twisted in the opposite direction to their single yarns to give a balanced structure.
Strength increases with twist up to an optimum and then falls, while more twist lowers spinning productivity and makes the yarn harder. Twist-lively yarns can snarl and cause spirality in knitted fabrics. Twist is measured by direct counting, as in ISO 2061, or by untwist and retwist methods for single spun yarns.
Key points
- Measured in turns per metre or per inch, with S or Z direction
- Twist multiplier relates twist to count for comparable character
- Warp yarns usually have more twist than weft or knitting yarns
- Strength peaks at an optimum twist and then falls
Where AiVibe comes in
AiAmbA use cases include visual inspection on textile and automotive lines, predictive maintenance and digital twins. Existing lines are retrofitted with edge devices, and AI agents only propose changes for a trained operator to confirm.
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