Unit 4: Fabric manufacturing
Elements of Textiles notes · PTU syllabus (BSTD 101-20)
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Unit summary
Yarns must be prepared before they can be woven, and looms must be understood to plan production. This unit covers preparatory processes for weaving, the motions of weaving and loom production calculations.
After this unit you can
- Describe warp and weft preparation
- Explain primary, secondary and auxiliary motions of weaving
- Name types of looms
- Calculate loom production and efficiency
PTU syllabus topics
- Preparatory processes for fabric manufacturing
- motions of weaving
- calculation of loom production
Shedding
Separates warp to open a shed
Picking
Passes weft through the shed
Beating-up
Reed pushes weft into the fabric
Secondary motions
Let-off and take-up
Topic 1
Preparatory processes for weaving
- 1Winding
Yarn transferred from bobbins to large cones; faults removed
- 2Warping
Many ends wound parallel onto a warp beam (direct or sectional warping)
- 3Sizing
Starch or synthetic size coats warp yarns for strength and smoothness
- 4Drawing-in
Each end threaded through drop wires, heald eyes and reed dents
- 5Weaver's beam
Mounted on the loom
- Weft preparation: pirn winding for shuttle looms; cones feed shuttleless looms directly.
Topic 2
Motions of weaving
Primary
Shedding
Separates warp threads into two layers to form a shed (tappet, dobby, jacquard)
Primary
Picking
Inserts weft through the shed
Primary
Beating-up
Reed pushes the weft into the fell of the cloth
Secondary
Take-up
Winds woven cloth and sets picks per inch
Secondary
Let-off
Releases warp at controlled tension
Auxiliary
Warp and weft stop motions, temples, brakes
Protection and quality
Shuttle loom
Shuttle carries a pirn
Slow, noisy; handloom and old powerlooms
Projectile
Small gripper projectile
Wide fabrics
Rapier
Rigid or flexible rapiers carry weft
Versatile; fancy yarns
Air-jet
Compressed air
Very fast; light fabrics
Water-jet
Water jet
Fast; synthetic filament fabrics only
Topic 3
Loom production calculations
Production (metres per hour)
(Picks per minute × 60 × efficiency) ÷ (picks per inch × 39.37)
Picks per cm
PPI ÷ 2.54
Efficiency
Actual production ÷ theoretical production × 100
Example
Loom at 600 picks per minute, 60 PPI, 85% efficiency: theoretical inches per hour = 600 × 60 ÷ 60 = 600 inches = 15.24 m; actual = 15.24 × 0.85 ≈ 12.95 m per hour, about 311 m per day (24 hours).
Key terms
- Warping
- Arranging many ends parallel on a beam
- Sizing
- Coating warp yarns to withstand weaving
- Shedding
- Separating warp threads to form a shed
- Picking
- Inserting weft across the warp
- Beating-up
- Pushing weft into the cloth with the reed
Quick revision
- Winding, warping, sizing, drawing-in; pirn winding.
- Primary (shedding, picking, beating-up), secondary (take-up, let-off), auxiliary motions.
- Shuttle, projectile, rapier, air-jet, water-jet looms.
- Production formula; efficiency.
Important exam questions
Practice questions written to the PTU exam pattern for this unit's syllabus: short answers (Section A style) and long answers (Sections B and C style).
Short-answer questions
- Q1.Why is warp sized?
- Q2.Name the three primary motions of weaving.
- Q3.What does the let-off motion do?
- Q4.Name two shuttleless looms.
- Q5.Calculate metres per hour at 400 ppm, 50 PPI, 100% efficiency.
- Q6.Define loom efficiency.
Long-answer questions
- Q1.Describe the preparatory processes for weaving.
- Q2.Explain the motions of weaving.
- Q3.Explain loom production calculations with an example.
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