1. SEWIING PROBLEMS

2. Factors contributing towards satisfactory seam
Good seams are essential factor in garment quality. Defective seam may spoil the appearance of a garment and they cause the garment ultimate failure.
Factors contributing towards satisfactory seam
type of seam
type of stitch
number of stitches per cm
selection of the type and size of sewing thread
choice of needle and
skill with which the fabric components are handle in assembly

3. Sewing problems can be divided into 3 categories as
Problems of stitch formation
(Poor seam appearance and performance)
Problems of damage to fabric along the stitch line
Problems of fabric distortion
(poor seam appearance)

4. The main problem which arise from the actual stitch formation are
Breakage of needle, bobbin or looper thread
Failure to form needle thread loop, or failure to pick up the needle thread loop
Skipped stitches
Staggered stitches
Unbalanced stitches
Variable stitch density

5. Breakage of needle thread
Breakage of needle thread can occur due to several reasons.
Incorrect threading
Excessive needle thread tension setting
Damaged hole in the throat plate
Damaged needle eye or groove
Thread entanglement
Low strength sewing threads
Incorrect timing of check spring
Needle heat
Poorly lubricated thread

6. Breakage of bobbin or looper thread
Sharp edges on the bobbin case tension spring
Rough surfaces and sharp edges in contact with the looper/bobbin thread

7. Failure to from needle thread loop, or failure to pick up the needle thread loops.
This can be due to
Incorrect needle length
(Causing the loop to form incorrectly and in the wrong position)
Wrong needle position
(Needle is not inserted correctly {too low down})
Incorrect rotary hook timing
(The point of the rotary hook misses the loop
because it approaches too early or too late)
Flagging
(The fabric rises with the needle and stops the loop being formed)

8. SKIPPED STITCH
stitch length is inconsistent possibly appearing as double the normal stitch length
threads in the stitch are not properly connected together.

9. Factors that Cause Skipped Stitches
Wrong thread for the application.
Quality defects in the thread.
Improper needle / thread size relationship.
Worn or defective thread guides or eyelets.
Improper threading.
Excessive machine thread tension.
Defective needle or improper positioning of the needle.
Improper feeding.
Improper operator handling.
Flagging.

10. Minimizing skipped stitches
Ensure proper machine maintenance and sewing machine adjustments
Make sure sewing machines are properly maintained and adjusted for the fabric and sewing operation.
Observe sewing operators for correct material handling techniques
Use a better quality sewing thread.

11. .
Staggered stitching Staggered stitching can be caused by yarns in the fabric deflecting needle away from a straight line of stitching, giving poor appearance.

12. Unbalanced stitches Lock stitches Where loops are seen either on the bottom side or top side of the seam. This is particularly evident with different coloured needle and bobbin threads, and where the stitch is too loose.

13. a) balanced
b) needle thread too tight/ bobbin thread too loose
c) needle thread too loose/ bobbin thread too tight

14. 401 Chain stitch Where the loops on the bottom side of the seam are inconsistent and do not appear uniform.

15. 504 Overlock stitch Where the needle loop is not pulled up to the underside of the seam and the "purl" is not on the edge of the seam.

16. a) balanced
b) lower looper thread too tight/ needle thread too loose
c) lower looper thread too tight/upper looper thread too tight d) upper looper thread too tight/lower looper thread too loose

17. Variable Stitch density
Variable stitch density arises from insufficient foot pressure in drop feed system, causing uneven feeding of the fabric through the machine.
It can occur particularly with materials with slippery surfaces. When stitching such materials specialized feeding systems (walking foot or differential feeding system) should be used to avoid such situations.

18. Problems of damage to the fabric along the stitch line
Fabric damage is a major problem in garment production
This type of problems can be of two different categories. They are
Mechanical damage
Needle heating damage

19. Mechanical damage When fabrics are seam together it is possible to damage the threads of the cloth. The problem of damage occurring during sewing as a result of the use of damage needles or of sewing unsuitable fabrics or combination of both. A needle where the point has become damaged may caused damage along the stitching line. The damage needle will cause the fibre or yarns to become broken.

20. This is not always apparent soon after sewing.
Mechanical Damage
This is not always apparent soon after sewing.
During wear the needle holes will become enlarged.
This cause damage to the fibers at the points of needle penetration.
This happens not only due to the needle but the machine speed and the type of fabric being sewn can also contribute to this problem.

21. There are several causes for mechanical damage due to the needle.
(i) Too large needle diameter for a given fabric
This causes the fibres to burst or separate as they are pierced by the needle. Use of small diameter needle can prevent this problem.
(ii) Too short length between the needlepoint and the eye
This type of problem can be prevented by using a suitable needle point. It causes for minimum distortion and reduces the possibility of cutting.

22. (iii) Usage of too blunt needle
This tends to carry the fabric into the needle hole with the danger of bursting. Possible action is changing the needle. If a medium or heavy ball point needle makes the damage, you can try with a set point or a light ball point needle.
(iv) Burr or hook on the needle
This is traceable by needle striking the presser foot, throat plate, and hook point, looper or needle guard during sewing.Possible solution is the replacement of the needle. If it occurs again, the removal of the corresponding burr on the metal part is necessary.
(v) Insufficient clearance in the needle hole in the throat plate.
To prevent the damage, the throat plate should be replaced with a correct size of the needle hole

23. Needle contact surface
Needle heating damage
The friction between the needle, the needle thread and fabric creates needle heat.
The following factors can have an impact on the amount of heat that is generated:
Fabric thickness
Fabric finish
Fabric color or density (darker colors normally are worse than lighter colors)
Sewing machine speed
Needle contact surface
-Needle Size or diameter
-Needle length
-Type of needle blade
-Type of needle finish

24. Needle holes caused by needle heat
Thread breakage due to needle heat

25. Different approaches to the problem of heating are possible
Preventing the heating occurring
Cooling down the needle as it heats
Preventing the heated needle from damaging the fabric or thread

26. Ways of Minimizing Needle Heat
Use a smaller diameter needle whenever possible. A smaller diameter needle will definitely minimize needle heat and may be the solution in marginal situations.
Use a “ball eye” needle. A “ball eye” needle is where the diameter across the eye is generally or .004 inch larger than the blade diameter.
On leather, vinyl, and other homogeneous fabrics, use a needle with cutting edges like a diamond, triangle, or wedge point.
Try needles with special low friction surfaces. Special needle coatings like Teflon or Tungsten will minimize the friction between the needle and the fabric.

27. Minimizing cont:
Use needle coolers or devices that blow compressed air on the needle during sewing.
Use a cotton wrapped polyester core spun thread. The cotton wrapper acts as an insulator protecting the thread from the heat.
Slow the sewing machines down to an acceptable level to minimize thread breakage due to needle heat.