Process Relationship Between Stitch Length, Fabric Weight / GSM and Fabric Width

1. Purpose / Amaç

This technical publication explains how Stitch Length / İlmek Boyu, Mass per Unit Area / Gramaj (GSM) and Fabric Width / Kumaş Eni should be assessed without reducing the result to a single machine setting.

The principal field rule is:

Finished GSM is not determined by stitch length alone. Yarn count, knit structure, active needles, stitch density, take-down, relaxation, wet processing, drying, stentering and compaction must be evaluated together.

The equations below are therefore diagnostic and control tools, not universal recipes.

2. Scope and Assumptions / Kapsam ve Varsayımlar

The discussion is based mainly on weft circular knitting. The same fundamental variables apply to single jersey, rib, interlock, lacoste, fleece, elastane-plated and tuck/miss structures, but structural coefficients and processing behaviour differ.

Valid comparisons require the following to be held constant:

• Fibre composition and yarn count
• Spinning system and twist
• Knit structure
• Machine diameter and gauge
• Active needle count
• Feeder and positive-feed settings
• Take-down
• Elastane draft
• Wet-processing and finishing route

3. Key Definitions / Temel Tanımlar

Symbol	Definition	Unit
l	Stitch Length / İlmek Boyu	mm/stitch
Lc	Course Length / Sıra Boyu	mm/course
Na	Active Needle Count / Aktif İğne Sayısı	count
T	Yarn Linear Density / İplik Lineer Yoğunluğu	tex
C	Courses per cm / Sıra Sıklığı	courses/cm
W	Wales per cm / Çubuk Sıklığı	wales/cm
S	Stitch Density = C x W	stitches/cm²
G	Mass per Unit Area / Gramaj	g/m²
Mf	Mass per Linear Metre / Lineer Metre Ağırlığı	g/m
B	Fabric Width / Kumaş Eni	m

4. Process Effect of Stitch Length / İlmek Boyunun Proses Etkisi

With yarn, structure, machine and finishing route held constant, increasing stitch length generally produces a more open geometry:

• Stitch density tends to decrease.
• GSM tends to decrease.
• Air permeability and openness may increase.
• Relaxed width may increase.
• Handle may become softer and looser.

Shortening stitch length generally produces the opposite tendency, while yarn tension, needle load and feeding balance become more critical.

Technical warning: Statements such as “longer stitch length always increases width” are incomplete. Finished width is the combined result of knitting width, relaxation, wet-process shrinkage, stenter width, overfeed and compaction.

5. Course Length / Sıra Boyu

For the basic case in which one yarn path forms one loop on every active needle in the relevant course:

Lc = l x Na

• Lc: course length, mm/course
• l: stitch length, mm/stitch
• Na: active needles knitting that course

Course length is a strong field-control parameter for yarn delivery and stitch length. The equation must be applied per feeder and per yarn path. Patterned structures, inactive needles, tuck/miss, plating, elastane or multiple yarn paths in one course require separate verification of active loops and yarn consumption.

6. Theoretical GSM Relationship / Teorik Gramaj İlişkisi

G_theoretical = (T x l x C x W) / 100

• T: tex
• l: mm
• C: courses/cm
• W: wales/cm
• G_theoretical: g/m²

For yarn count in English cotton count:

tex = 590.5 / Ne

The equation may require structural corrections for tuck/miss, multiple yarns, plating, elastane, pile yarns, chemical add-on, fibre loss and relaxation. It does not replace measured GSM.

7. Worked Example / Hesaplama Örneği

Data:

• Yarn: 30 Ne cotton
• Stitch length: 2.80 mm
• Courses: 20 courses/cm
• Wales: 14 wales/cm
• Relaxed open width: 1.68 m

T = 590.5 / 30 = 19.68 tex
S = 20 x 14 = 280 stitches/cm²
G_theoretical = (19.68 x 2.80 x 20 x 14) / 100
G_theoretical = 154.3 g/m²

Mass per linear metre:

Mf = G x B
Mf = 154.3 x 1.68
Mf = 259.2 g/m

If the same linear mass is spread to a width of 1.74 m:

G = Mf / B
G = 259.2 / 1.74
G = 149.0 g/m²

This demonstrates that GSM changes not only through knitting settings but also through the finished area over which the same mass is distributed.

8. Width–GSM–Linear Mass Relationship / En–Gramaj–Lineer Metre İlişkisi

Mf = G x B
G = Mf / B
B = Mf / G

Units:

• Mf: g/m
• G: g/m²
• B: open-width fabric width, m

Tubular-fabric warning: If B is the laid-flat tubular width, one linear metre has two fabric faces. The effective area is therefore approximately based on 2 x B:

Mf_tube = G x 2 x B_flat
G = Mf_tube / (2 x B_flat)

This relationship is especially useful after stentering and compaction. Linear mass must not be assumed constant if edge trimming, process loss, moisture variation or chemical add-on occurs. The record must always state whether width is open width or laid-flat tubular width.

9. Stage-to-Stage Mass–Area Balance / Prosesler Arası Kütle–Alan Dengesi

G2 = G1 x Rm / (Rw x Rl)

• Rm = M2 / M1: mass-retention ratio
• Rw = B2 / B1: width ratio
• Rl = L2 / L1: length ratio

Example:

G2 = 180 x 0.98 / (1.04 x 0.96)
G2 = 176.7 g/m²

This approach allows width, length and mass changes to be assessed together across pretreatment, dyeing, drying, stentering and compaction.

10. Measurement and Sampling Plan / Ölçüm ve Numune Alma Planı

Process stage	Mandatory measurements
Machine delivery	Course length, stitch length, tube width, take-down, feed setting
Relaxed greige	Width, GSM, courses/cm, wales/cm, spirality
After pretreatment	Width, GSM, length change, pH, process loss
After dyeing	Width, GSM, shrinkage tendency, within-lot variation
After stenter	Finished width, overfeed, exit moisture, GSM
After compactor	Width, GSM, length shrinkage, compaction setting
After laundering	Lengthwise and widthwise dimensional change, spirality

Samples should be measured without tension after a defined relaxation period. GSM comparisons must use consistent conditioning and moisture conditions.

11. Defect–Root Cause–Corrective Action / Hata–Kök Neden–Düzeltici Faaliyet

Observation	Possible root causes	Verification	Corrective action
High GSM	Short stitch length; narrow width; high overfeed/compaction; coarser yarn; excessive wet-process shrinkage	Measure stitch length, linear mass, width and density together	Conduct a controlled one-variable trial while protecting width and shrinkage targets
Low GSM	Long stitch length; excessive width; insufficient compaction; finer yarn; low stitch density	Verify tex/Ne, course length, C, W and finished width	Correct feeding/take-down and finishing stepwise after confirming yarn and structure
Low width	Short stitch length; high take-down; wet-process shrinkage; narrow stenter width; excessive compaction	Trend greige, relaxed, dyed and finished widths	Correct the process stage where the deviation begins; do not hide it only by opening the stenter
High width and low GSM	Long stitch length; excessive stenter width; low overfeed; insufficient compaction	Check linear mass and width at the same stage	Optimise width, GSM and dimensional stability together
Within-lot GSM variation	Feeder variation, yarn count/moisture variation, unstable take-down, stenter width/moisture variation	Feeder-based course-length checks and roll-based control charts	Feeder calibration, yarn-lot control and process SPC

12. Shop-Floor Control Sequence / Saha Kontrol Sırası

1. Verify fibre, yarn count, twist, lot and moisture.
2. Verify machine diameter, gauge, active needles, feeders, cams, positive feed and take-down.
3. Measure course length; do not rely only on machine-display settings.
4. Measure relaxed greige fabric; machine-delivery width is not the acceptance width.
5. Monitor linear-metre mass together with GSM.
6. Separate process stages; do not hide a knitting deviation at the stenter.
7. Change one variable at a time.
8. Confirm the result after laundering and dimensional-stability testing.

13. Technical Warning on Tolerances / Toleranslar Hakkında Teknik İkaz

No universal stitch-length, GSM or width tolerance is specified here. Tolerances must be defined for each product using:

• structure,
• yarn and elastane system,
• customer specification,
• machine repeatability,
• process capability,
• sampling method.

14. References / Kaynaklar

1. CottonWorks — Stitch Length
2. CottonWorks — Course Length
3. CottonWorks — Knit Machinery
4. CottonWorks — Shrinkage & Skewing
5. CottonWorks — Proper Processing of 100% Cotton Knit Fabrics
6. ASTM D3776/D3776M — Mass Per Unit Area of Fabric
7. ISO 139:2005 — Standard Atmospheres for Conditioning and Testing
8. ISO 22198:2006 — Determination of Fabric Width and Length
9. ISO 3759:2011 — Preparation, Marking and Measuring for Dimensional Change
10. ISO 6330:2021 — Domestic Washing and Drying Procedures
11. AATCC TM135-2025 — Dimensional Changes after Home Laundering
12. Flexible Theoretical Calculation of Loop Length and Area Density of Weft-Knitted Structures