Stitching problems and causes in sewing.ppt

Problems in stitching and causes

1. Quality issues & Solutions

2. STITCHING QUALITY MEASUREMENT
STITCH SIZE
STITCH TENSION
STITCH SEQUENCE
ELONGATION
ELASTICITY
RESILIENCE
FABRIC DISTORTION
STRENGTH (TENSILE & ABRASION)
YARN SEVERENCE

3. SEAM QUALITY MEASUREMENTS
SEAM SIZE
SEAM SLIPPAGE STRENGTH
SEAM STRENGTH

4. SEAM SIZE
SEAM DEPTH – thickness &
compressibility
SEAM LENGTH
SEAM WIDTH

5. SEAM SLIPPAGE STRENGTH
Amount of force required to pull out a total of
0.25” of the opposing set of yarns perpendicular
to the seam line.
Standard seam conditions for Seam Slippage test
(ASTM Test D 434-42)
Stitch type no. 301, 12 spi
SSa -1 seam, 0.5” width
Mercerized cotton thread
Approx. 0.03” needle diameter

6. Seam quality issues
1. Puckering
2. Seam grin
3. Seam slippage
4. Skipped stitches
5. Unbalanced stitches
6. Uneven SPI

7. Skipped Stitches
Causes Solutions
Failure of hook, looper, or needle to enter
the thread loop at correct time
Check machines clearances and timing.
Check needle is inserted and aligned correctly
Use needle with deeper scarf.
Thread loop failure
Change needle size/style
Check thread take-up and check loop formation
Flagging of fabric due to poor presser foot
control or too large a throat plate hole
Adjust presser foot pressure
Change throatplate to match needle
Needle deflections or bent needles
Use a reinforced needle
Check needle clearance and reset needle guard
Incorrect sewing tension in needle or under
thread
Adjust thread tension
Poor loop formation
Check loop formation
Verify thread selection
Check thread twist and thickness

8. Variable Stitch Density
SolutionsCauses
Poor fabric feed control
Increase presser foot pressure
Change to a more positive feed mechanism

9. Seam Grin
 When two pieces of fabric are pulled at right angles to the
seam, a gap is revealed between the two pieces of fabric
revealing the thread in this gap.
 Corrective actions

Increase stitching tensions

Use a higher stitch rating

10. Seam Slippage
A fabric related issue.
 Happens mainly in 2 types of fabrics :

fabrics with low no. of warp & weft yarns.
 fabrics where C.F. yarns are used in the
weave.
 The fabric on either side of the seam
distorts as the fabric yarns slide away
resulting in a permanent gap.
 Corrective Actions
 Increase seam allowance
 Use a higher stitch density
 Opt for a lapped fell seam

11. Seam Pucker

Tension pucker

Feed pucker

Shrinkage pucker

Inherent pucker

Fabric flagging

12. Tension Pucker
 Caused by high thread tension during sewing.
 More pronounced when synthetic threads are
used.
 These threads on account of high stretch
properties elongate more during sewing.
 After sewing the threads recover from the stretched
state pulling the fabric with it.
Remedy:
Thread tensions have to be kept as
low as possible.

13. Feed Pucker
 Encountered when sewing very fine fabrics.
 The plies of fabric tend to slip over each other
resulting in uneven feed leading to pucker.
Remedy :

Opting for advanced types of feed
systems like compound or unison feed.

Puller feed is more cost effective.

14. Shrinkage Pucker
 Wash pucker - during the wash process the thread in the seam
shrinks, pulling the fabric with it. More so when using cotton
threads.
 Ironing pucker - normally happens when synthetic threads are
used. The heat destabilizes the molecular structure of the
thread causing it to contract.
Remedy
 Choosing threads with low shrinkage properties.

15. Inherent Pucker
 Normally seen when sewing densely woven materials.
 This occurs because the needle forcibly displaces the
warp & weft ends of the dense weave to a significant
extent.
 These displaced ends are pushed upwards to the
surface of the fabric and appear as pucker.
 This is also know as 'STRUCTURAL JAMMING'
Remedy

Opting for finer needles & threads

Opt for a chain stitch in place of a lock
stitch

Reduce stitch density

Biased stitching

17. Fabric Flagging
 A machine related issue
 the throat plate aperture enlarges due to wear & tear
 while sewing the needle pushes the fabric through the
aperture before penetrating the fabric
 this can also happen when the needle size (thickness) is
changed and if the throat plate is not changed accordingly.
Remedy

throat plates must be changed at regular intervals
after checking for wear & tear

throat plates must be changed in accordance with the
needle size even if there are no signs of wear & tear.
Needle Size - Nm 60 65 70 80 90 100 110 120
Throat plate - Nm 100 120 120 140 160 160 200 200
aperture size

40. Garment / Seam properties

41. A garment is made up using a series of different seams.
Therefore, a thread should be chosen for specific seams to ensure
maximum benefits.
Seam Engineering

Seam appearance
ƒ Is the seam attractive, consistent, and neat?

Seam strength
ƒ Have the correct seam type and thread selections
been made for the item being sewn?

Seam stretch
ƒ Does the seam allow stretch especially in high
elongation fabrics viz : knits, lycra blends

Seam durability
ƒ Do the properties of the seam, thread, and fabric
lend themselve to the desired length of use for the
item sewn?

42. Seam Strength
Critical factors :
 Fabric type and weight.
Thread fiber type, construction, and
size.
Stitch and seam construction.
Stitches per inch.
Stitch balance.
Seam strength = SPI X STS X 1.5 - lockstitch
SPI X STS X 1.7 - chainstitch
e.g.
for a seam with a density of 16 spi & a thread with a 1100 gms STS
seam strength for lockstitch = 16 X 1100 X 1.5 = 26,400 gms.
= 26. 4 kgs
seam strength for chainstitch = 16 X 1100 X 1.7 = 29,920 gms.
= 29. 9 kgs
The seam is sewn at right angles
to the direction of load.

43. Seam Strength
 Stitch Type
ƒ The lockstitch is the most common stitch used, but the most easily
damaged.
ƒ Chain and overedge stitches offer more extensibility, which leads to
more resistance to stress.
 Stitch Density
ƒ Seam strength is usually proportional to stitch density.
ƒ Increasing stitches per inch gives a stronger seam up to a point.
Sometimes it is more economical to use a stronger thread.
 Seam Type
ƒ A lap felled seam is the strongest of all seam types because the
fabric is lapped upon itself and shares the stress load along with
the thread. However, the lap felled seam makes a bulky seam.
ƒ A butt seam is designed to maintain a flat profile, but in this type
seam the thread bears the entire load of stress in the seam.

44. Seam Stretch
Critical factors
 Thread extensibility
 Stitch type
 Stitch rating
 Fabric Type
Seam stretch is expressed as a % .
The seam is sewn parallel to
the direction of load.

45. Seam Durability
Defined as the ability of a seam to withstand
abrasion during :
 Distress garment washes like stone, sand, golf ball etc.
 Normal machine wash
 Day to day wear & tear of a garment
Durability factor for various substrates :
 Rayon: 1
 Cotton: 3
 SSP: 12
 Core spun : 30
 CF Nylon : 150

46. THANK YOU