Knit Fabric Construction: Single Jersey, Rib, Interlock & Fleece
Lesson Contents Overview
Learning Objectives
Comprehensive Technical GuidanceTextbook & Training SOP
Knit Fabric Construction: Single Jersey, Rib, Interlock & Fleece
═══════════════════════════════════════════════════════════════════════════════ MODULE 03: KNIT VS WOVEN FABRIC CONSTRUCTION LESSON 03.01: KNIT FABRIC CONSTRUCTION: JERSEY, RIB, INTERLOCK & FLEECE ═══════════════════════════════════════════════════════════════════════════════ [Course: Yarn Count Conversion & Textile Mathematics] [⏮️ Prev: 02.03 Yarn Strength CSP] [Next: 03.02 Woven Fabric Weaves ⏭️]
1. Fundamentals of Weft Knitting & Loop Geometry
A weft-knitted fabric is constructed by needles drawing loops of yarn horizontally across adjacent vertical columns called wales, forming successive horizontal rows called courses.
┌─────────────────────────────────────────────────────────────────────────────┐ │ BASIC KNITTED LOOP GEOMETRY │ │ │ │ [NEEDLE LOOP HEAD] │ │ ╭───────╮ │ │ ╭╯ ╰╮ │ │ [WALE] │ │ ◄── Loop Leg (Right & Left) │ │ (Vertical │ ╭───╮ │ │ │ Column) ╰──╯ ╰──╯ │ │ [SINKER LOOP / FEET] ──► Connects to adjacent loop │ │ ◄───────────────────► │ │ [COURSE] (Horizontal Row) │ └─────────────────────────────────────────────────────────────────────────────┘
- Wales Per Inch (WPI): Governed by machine gauge (needles per inch) and horizontal fabric relaxation.
- Courses Per Inch (CPI): Governed by yarn feed rate, takedown tension, and loop length ($l$).
- Stitch Density ($S$): Total loops per square inch: S = CPI × WPI
2. Core Weft Knit Fabric Structures
┌─────────────────────────────────────────────────────────────────────────────┐ │ MAJOR WEFT KNIT STRUCTURE COMPARISON │ ├───────────────────┬───────────────────┬───────────────────┬─────────────────┤ │ STRUCTURE │ NEEDLE BEDS │ FACE VS BACK │ EDGE BEHAVIOR │ ├───────────────────┼───────────────────┼───────────────────┼─────────────────┤ │ 1. Single Jersey │ 1 Bed (Cylinder) │ Face: V-wales │ Strong curling │ │ │ │ Back: Purl semic. │ to technical face│ ├───────────────────┼───────────────────┼───────────────────┼─────────────────┤ │ 2. 1x1 / 2x2 Rib │ 2 Beds (Cylinder │ Identical both │ Completely flat │ │ │ & Dial) │ sides (Alternating│ (Zero edge curl)│ ├───────────────────┼───────────────────┼───────────────────┼─────────────────┤ │ 3. Interlock │ 2 Beds (Alternate │ Identical smooth │ Completely flat │ │ │ Interlock gating) │ face on both sides│ (High stability)│ ├───────────────────┼───────────────────┼───────────────────┼─────────────────┤ │ 4. 3-End Fleece │ 1 Bed (3 feeds │ Face: Jersey │ Flat after │ │ │ per feeder) │ Back: Floating loop│ finishing │ └───────────────────┴───────────────────┴───────────────────┴─────────────────┘
3. Loop Length ($l$) & Tightness Factor ($K$)
The loop length ($l$ in mm) is the single most critical knitting machine variable controlling fabric weight (GSM).
The Tightness Factor ($K$) indicates how tightly the loops are packed:
K = Texl (in cm)
- Normal Range: 13.0 ≤ K ≤ 15.0
- $K < 13.0$: Loose, open structure with low recovery and high shrinkage.
- $K > 15.5$: Overly tight structure prone to needle cutting and harsh hand feel.
4. Visual Asset Generation Prompt
5. Summary & Key Takeaways
- Loop Geometry: Knits consist of wales (vertical) and courses (horizontal) with stitch density S = CPI × WPI.
- Single vs Double: Single jersey curls and unravels from top; Rib and Interlock are double-knit, non-curling, and balanced.
- GSM Control: Loop length ($l$) and machine gauge are the primary determinants of finished knit fabric weight.
1. Master Comparison of Major Weft Knit Fabric Structures
| Fabric Structure | Needle Beds Used | Face vs Back Appearance | Lateral Stretch (%) | Edge Curling Behavior | Typical Finished GSM | Common Apparel Applications |
|---|---|---|---|---|---|---|
| Single Jersey | Single Cylinder (1 Bed) | Face: V-loops (Wales); Back: Purl semicircles (Courses) | 40% – 60% | High (Curls to face at sides, to back at ends) | 120 – 200 GSM | T-shirts, basic tops, underwear, bedsheets, activewear |
| 1x1 Rib | Cylinder & Dial (2 Beds) | Identical on both sides (Alternating 1 face wale, 1 back wale) | 80% – 120% | Zero (Lies completely flat) | 180 – 260 GSM | T-shirt neck ribs, sleeve cuffs, tank tops, polo collars |
| 2x2 Rib | Cylinder & Dial (2 Beds) | Alternating 2 face wales and 2 back wales (Broad rib lines) | 100% – 150% | Zero (Lies completely flat) | 200 – 300 GSM | Heavy sweater hems, jacket waistbands, sock tops |
| Interlock | Cylinder & Dial (Interlock Camming) | Smooth, compact, and identical on both face and back | 30% – 50% | Zero (Lies completely flat) | 200 – 320 GSM | Babywear, high-end polos, leggings, dresses, golf shirts |
| Pique / Lacoste | Single Cylinder (Tuck Cams) | Honeycomb / waffle textured face, flat backing | 30% – 45% | Low / Moderate | 180 – 240 GSM | Classic polo shirts, athletic tennis shirts, corporate uniforms |
| 3-End French Terry | Single Cylinder (3 Feeds/Feeder) | Face: Smooth jersey; Back: Extended loop inlay (Unbrushed) | 25% – 40% | Low | 240 – 340 GSM | Casual joggers, lightweight sweatshirts, lounge shorts |
| 3-End Polar Fleece | Single Cylinder + Napping M/C | Face: Jersey/Brushed; Back: Heavily napped/raised plush pile | 20% – 35% | Zero | 280 – 420 GSM | Winter hoodies, heavy track jackets, thermal blankets |
2. Recommended Machine Gauge (E) vs. Yarn Count (Ne) Selection Guide
| Machine Gauge (E / GG) | Needles per Inch | Single Jersey Suitable Ne | 1x1 Rib Suitable Ne | Interlock Suitable Ne |
|---|---|---|---|---|
| 14 Gauge (14G) | 14 needles/inch | 10s – 14s Ne | 12s – 16s Ne | 16s – 20s Ne |
| 18 Gauge (18G) | 18 needles/inch | 16s – 20s Ne | 18s – 24s Ne | 24s – 30s Ne |
| 20 Gauge (20G) | 20 needles/inch | 20s – 24s Ne | 24s – 30s Ne | 30s – 36s Ne |
| 24 Gauge (24G) | 24 needles/inch | 24s – 30s Ne | 30s – 36s Ne | 36s – 42s Ne |
| 28 Gauge (28G) | 28 needles/inch | 30s – 38s Ne | 36s – 45s Ne | 40s – 50s Ne |
| 32 Gauge (32G) | 32 needles/inch | 40s – 50s Ne | 45s – 60s Ne | 50s – 65s Ne |
| 36 Gauge (36G) | 36 needles/inch | 50s – 60s Ne | 60s – 80s Ne | 60s – 80s Ne |
Practical Commercial Flow
A knit fabric manager in Dhaka is setting up a Mayer & Cie 30-inch diameter, 24-Gauge (24G), 96-feeder circular knitting machine to knit 180 GSM finished single jersey for polo t-shirts:
Factory Real-Life Scenario
Scenario: A sportswear factory experienced severe laddering/runs and edge curling during automated cutting of activewear leggings made from a proposed single jersey fabric.
Solution: The textile technologist switched the fabric construction from single jersey to an Interlock structure (40/1 Ne Combed Cotton + 40D Spandex on a 32-gauge double-knit interlock machine).
Impact: The interlock fabric eliminated edge curling entirely, doubled fabric opacity (preventing "sheer through" on stretching), and increased garment sewing productivity by 22% on automated assembly lines.
Commercial Officer Best Practice
In circular knitting QA, always inspect the stitch length ($l$ in mm) from all 4 or 6 yarn feeder sections. A 0.05 mm variation in loop length between feeders creates horizontal feeder stripes (barre marks) that become visible after piece-dyeing.
Top Beginner Mistakes to Avoid
- Using high-twist weaving yarn for circular knitting, resulting in severe fabric spirality (torque >10%) and skewed side seams.
- Allowing feeder-to-feeder loop length variation greater than 1.5%, which creates visible horizontal banding (feeder barre).
- Confusing Interlock with 1x1 Rib: Interlock requires specialized synchronized long/short needles and has an identical smooth face on both sides, whereas Rib has alternating vertical wales and much higher lateral stretch.
- Failing to adjust fabric takedown tension between light single jersey and heavy 3-end fleece, causing needle press-offs or stretched greige rolls.
- Selecting an inappropriate yarn count for machine gauge, leading to latch spoon breakage or loose, flimsy fabric.
Important Commercial & Trade Terminology (6 Terms)
A vertical column of knitted loops formed by the same needle in successive knitting cycles.
💡 Note: Wales per inch (WPI) measures horizontal density.A horizontal row of knitted loops formed by adjacent needles across the width of the fabric in a single revolution or traverse.
💡 Note: Courses per inch (CPI) measures vertical density.The total length of yarn contained in a single knitted loop, measured in millimeters (typically 2.4 mm to 3.2 mm).
💡 Note: Primary control parameter for fabric GSM.The number of knitting needles per linear inch along the circumference of the needle cylinder or dial.
💡 Note: Higher gauge = finer needles and finer knit.A knit structure where a needle receives a new loop without clearing its previous loop, producing a thicker, wider fabric with surface texture (e.g. Pique).
💡 Note: Used in Lacoste polo fabrics.A knit structure where a needle misses yarn feeding, leaving a straight yarn float on the technical back.
💡 Note: Used in jacquards and fleece inlay.Interview Preparation Questions & Answers (3 Questions)
Master these high-frequency interview questions for Commercial Officer, Merchandising, and Export Executive roles.
In Single Jersey, all loops are pulled in the same direction (towards the technical face), creating unbalanced internal three-dimensional elastic bending moments. The vertical edges curl towards the face (due to wale loop curvature) and horizontal edges curl towards the back (due to course yarn curvature). In 1x1 Rib and Interlock, face and back loops alternate symmetrically across the two needle beds. The opposing elastic bending forces cancel each other out perfectly, resulting in zero net torque and a completely flat, non-curling fabric.
Frequently Asked Questions (3 FAQs)
Clear, beginner-friendly answers to the most common questions about the Commercial Department.
Key Takeaways & Summary Points
Executive Lesson Summary
Weft-knitted fabrics represent a vast sector of apparel production. By mastering loop mechanics, machine gauge dynamics, and structural distinctions between Single Jersey (curling, lightweight), Rib (elastic, reversible), Interlock (stable, smooth, double-knit), and Fleece (insulating 3-end structure), textile technologists engineer knits with precise GSM, stretch, hand feel, and sewing performance.
Lesson Downloads & SOP Templates
Fabric GSM Calculator
Calculate knit fabric GSM from loop length, courses, and wales.
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