Weaving and Knitting
This domain tests loom and knitting-machine mechanics: the named motions, which device makes which motif size, and the vocabulary of loop structure (wale, course, stitch density).
Loom motions
- Primary: shedding, picking, beat-up. These three make cloth.
- Secondary: let-off (warp supply) and take-up (fabric draw-off).
- Tertiary: warp stop motion, weft stop motion, temples, selvedge cutters - they protect quality, not structure.
- Shedding devices: tappet/cam for simple repeats, dobby for small geometrics, jacquard for large pictorial motifs because each hook controls an individual end.
Knitting
- Weft knitting: single jersey (face and back differ), rib 1x1, interlock. Warp knitting: tricot and raschel.
- Wale = a column of loops; course = a row of loops. Stitch density = wales per cm x courses per cm.
- Machine gauge E = needles per inch; higher E means finer fabric.
Worked example
A loom runs at 300 picks/min weaving a fabric with 40 PPI at 85% efficiency. Find hourly output. Picks per minute effectively inserted = 300 x 0.85 = 255. Weft consumed = 255 / 40 = 6.375 inches/min = 16.2 cm/min. Output = 16.2 x 60 = 972 cm/h, about 9.7 m/h. Reasoning: efficiency is applied to loom speed first, then converted to fabric length via PPI.
Traps that cost marks
- Listing warp stop motion as a primary motion.
- Claiming a dobby can weave a large floral pictorial motif; that needs a jacquard.
- Reversing wale and course.
- Forgetting that let-off and take-up are secondary motions, not tertiary.
- Applying efficiency after conversion when the question asks for picks inserted per minute.